Archive for the ‘Virtualization’ category

VMware VCAP5-DCA Exam Experience

November 7th, 2013

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For quite some time I’ve had it on my agenda to sit the VMware Certified Advanced Professional Datacenter Administrator (VCAP5-DCA) exam.  It was starting to bother me and since I hadn’t sat a VCAP5 exam since June of last year (the DCD) and because I didn’t want to let the upgrade path lapse, it was time.  So a month ago I scheduled the exam looking for the next available slot across three different Pearson VUE testing centers in the Twin Cities.  First available was 8am Wednesday November 6th.  So by now you’ll know what this blog post is about.

VCAP exams aren’t impossible but they aren’t easy either.  There’s a time investment in the preparation plus half a day spent in the exam room.  Then there is the price tag of the VCAP exam which stings but the sting is far worse if you have to pay the same again fee for a 2nd attempt.  I’ve taken four of them in the past and on each one, I’ve been challenged by the time management component as are many others.  I had spoken to a few others over the past six months and each of them were consistent in painting the same picture of their own experience in that they did not complete the exam or came nowhere close to completing before running out of time.  Now while it is still possible to pass the exam without actually finishing it, obviously points are left on the table and I didn’t want that to be a deciding factor on my own success or failure.

So I decided to once again up my strategy for a VCAP exam.  Instead of simply being conscious of time on the exam – in other words knowing when I need to move on to the next question, I wanted to improve my pace by increasing the tempo at which I work without sacrificing accuracy and hopefully without advancing to the next question before all tasks on the previous question were completed.  In the past I might have gone into the exam room without preparing as much as I really should have (I’ve been known to do that with VCAP beta exam attempts).  Instead I just relied on the skills I had built up to that point.  While that strategy mostly worked, I also spent a lot of precious time in deep thought over questions here and there because I hadn’t prepared enough for the breadth and depth of skills that were being measured.  That leads to running out of time before completing all of the questions on the exam and I didn’t want to go that route this time.

To accomplish this I needed to dig deep into the blueprint and really attack the weak areas, as unsexy as they may be.  Taking a look at the VCAP5-DCA blueprint, it wasn’t quite that bad but clearly there were a few areas I needed sharpen up on especially since I’ve been out of day to day management of large vSphere infrastructures for a few years which naturally kept me sharp enough at the time.  Fortunately I came across a fantastic study guide by Jason Langer and Josh Coen and sponsored by Veeam who has been nothing but great to the vCommunity.  I would summarize this 237 page guide as being balls-on dead-accurate as far as what you need to know for the exam (that said, the exam itself mapped very well to the blueprint – no surprises whatsoever).  These guys really did a great job in compiling all of the blueprint subject matter in one spot.  Often times there are multiple tools or methods to complete a task and this is true in the VCAP exam room.  Team Langer and Coen demonstrate the multiple methods available.

Another good resource I looked at is Rick Scherer’s VMware vSphere 5.0 Auto Deploy video on YouTube.  I’ll be honest – I haven’t been overly impressed with Auto Deploy and as such I never invested much time in all the PowerShell memorization required to build the depots, images, and rules for stateless ESXi deployment.  Bottom line here is it’s clearly on the exam blueprint and if you want to score some points on Auto Deploy, you must learn how to build, configure, and manage it.  Rick’s 30 minute video is no-nonsense and moves at a brisk pace making it look pretty easy actually.  Did I get it all memorized? Not quite but I knew how to grab at least a few points by setting up DHCP/GPXE, building the depot, adding custom VIBs, and cloning profiles and exporting either images or repositories.

Next is Canadian eh? Mike Preston who is building a great series called 8 weeks of VCAP.  Over there you’ll find some good content on Host Profiles, Auto Deploy, as well as other blueprint content.  Mike tells it like it is and has fun with it.

Last but not least, I took a look at Michael Webster’s blog post on his VCAP5-DCA experience.  It’s a good writing and buried within you’ll uncover several great tips for this particular exam that either he came up with or he learned from others.  I used those tips in the exam room this morning.  For instance, the tip about only using the vSphere Client from the first/main RDP session where the toolbar exists (as opposed to an RDP session into the vCenter Server and then launching the vSphere Client and subsequent Remote Consoles from there – it starts getting nasty with sessions within sessions within sessions).  Of course his bit on time management is dead-on accurate.  He also mentions the potential danger in skipping too many tasks.  While not all labs and tasks build on each other, a fair amount of them do.  If you do skip a task and need to go back, you can go backwards in the exam which is good but would chew up more valuable time.  Based on my exam experience, I would surmise that if one were to completely skip all tasks which had interrelated dependencies, it would be enough to fail.  That said, of course I don’t know VMware’s scoring rubric – it’s just a guess.  He also mentions the environment isn’t perfect.  That’s true and will likely vary from kit to kit.  I discovered a few items which impacted my results and I would guess weren’t designed to be part of the lab.  Unfortunately I was offered no areas to submit exam/lab feedback so I left the lab scoring proctor a nice long letter in the ‘notes’ field of one of the virtual machines hoping he/she would see it when scoring was performed on that particular VM.

All of the above is very helpful.  I would add that if you’re already good at most of the day to day garden variety vSphere administration with a mouse, explore some territory not often visited.  For example, step away from the familiar GUI tools and spend a day or two immersed in vCLI and/or PowerShell.  On the vCLI side of the house, one command you’ll want to get to know well is esxcli, particularly the pluggable storage architecture (PSA) components and management.  While most people probably use the vSphere Client or a vendor plug-in to manage their shared storage, you’ll need to understand the moving parts and how to accomplish the same tasks and more via CLI.  It might sound crazy but there is a level of satisfaction and appreciation making a datastore disappear and reappear with some MASK_PATH command line work.  There is also a good chunk of storage device management that can be performed using CLI where there is no GUI equivalent short of a storage vendor plug-in and I haven’t come across one yet that goes into that level of detail.  If it’s not completely obvious by now – you have to have a lab environment to work in.  As one of the resources above points out, you don’t need an enterprise lab, but you do need a pair of vSphere hosts that can run at least five VMs plus some flavor of shared storage, preferably block if choice must be made between block or file but best case scenario you have both available as the exam does have some NFS coverage.

 

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Exam Format:

  • 26 live labs, each with multiple tasks varying in quantity and difficulty
  • 220 minutes for native English speakers
  • A fair amount of reading and comprehension but not overload
  • No coffee in the exam room
  • $400US (but I had a discount voucher for this one)

I wouldn’t say I studied long but I studied hard on the focus areas that needed attention.  I worked hard in the lab, did some whiteboarding to test memory retention, and it paid dividends.  I was able to move through the VCAP5-DCA exam swiftly and I was pretty shocked to have reached the end with a few minutes to spare.  I’ll go so far as to say I was actually enjoying myself for the first time in a long time in an exam room.  It certainly helps knowing the content well which in turn builds confidence through each of the completed labs.  Conversely, not knowing the material makes for an increasingly dismal situation as the exam progresses.  Did I make some mistakes?  Yes I made a few which I realized later in the day as I spent time reflecting.  I’d like a 2nd shot at those but it’s water under the bridge now.  While saying I reached the end with some time to spare is accurate, I need to qualify that with the fact that I skipped two labs which were going to be time intensive and potentially error prone.  I made the call to skip them in the interest of seeing more of the exam before running out of time.  Discounting those two labs, I did complete more of the exam than I actually expected and for that I am quite pleased.  I would say my approach of time and tempo management this round was a success.

So now I wait 15 business days for my results from VMware.  I feel confident but one never really knows with these exams.

Update 11-20-13: I received a passing grade from VMware this morning but I haven’t seen a score yet. That may come later.

Announcing the Mastering vSphere 5.5 Book Winners

November 1st, 2013

Snagit CaptureUpon returning from VMworld 2013 San Francisco, I kicked off a contest with an award pool containing five copies of the upcoming Mastering vSphere 5.5 book.  Amazon is reflecting an in-stock date of November 3rd and I’ve seen at least one mention on Twitter from an author that he has received his hard copy.  My pre-orders should be arriving soon and I should announce the winners of the contest.

A few details:

  1. My name is written in green approximately in cell AD4 along with the inscription “VMware is my life and passion”
  2. The contest entries came in very quickly and there were five winners inside of two hours or less.
  3. By design, I kicked off the contest late at night to give folks across the pond and on the other side of the world a chance.  From what I can tell, most of the winners are not from this continent so I’ll be sending books overseas.  Please be patient for their arrival.

And now the moment everyone has been waiting for – the winners are:
Nick Carbone, appears to be from LA
David Wilde, I’m guessing UK
Seb, somewhere in the UK
Fernando Martinez, Mannheim, Germany
Conor Buckley, Cork, Ireland

Thank you to all who participated and my congratulations go out to the winners.  I’ll be contacting each of you via email for your shipping address.

VCA-WM Exam Review

October 21st, 2013

Last Thursday while on vacation in Tucson, Arizona, I sat the VMware Certified Associate – Workforce Mobility exam (exam code VCAW510).  This is the third of three currently available VCA level exam I’ve attempted in the last three weeks.  I wrote about the previous VCA exam experiences here and here.

VMware’s take on VCA-WM preparation:

There is no training requirement, however there is a free, self-paced elearning class that can help you prepare.

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VMware summarizes the VCA-WM certification as follows:

With the VCA-Workforce Mobility certification, you’ll have greater credibility when discussing workforce mobility and end-user computing, the business challenges that VMware Horizon Suite is designed to address, and how deploying the Horizon solution addresses those challenges. You will be able to define workforce mobility and provide use case scenarios of how Horizon and workforce mobility can deliver freedom, flexibility, and manageability while connecting people to their data, applications, and desktops.

VMware further explains that a successful candidate who passes the VCA-WM will realize the following benefits:

  • Recognition of your technical knowledge
  • Official transcripts
  • Use of VCA-WM logo
  • Access to the exclusive VCA portal & logo merchandise store
  • Invitation to beta exams and classes
  • Discounted admission to VMware events
  • Greater opportunities for career advancement

Once again, I recognize two additional benefits to this exam experience:

  • The exam can be taken online from any location with a compatible internet web browser and an internet connection
  • By virtue of the above, coffee is available in the exam room – those who know me know this is a perk

Chris Wahl has a new blog post introducing The New VMware Certified Associate (VCA) Exams.  His video includes VCA exam background, preparation, as well as step by step instructions covering exam registration.

Length for native English speaking vGeeks is 50 questions in 75 minutes.  Both multiple choice and multiple select style of questions.  VMware’s exam summary was consistent with my exam experience.  While I don’t design and manage VMware VDI environments on a daily or even semi-regular basis, I’ve managed one in my own lab for the past few years and I’m familiar with all of the components in the Horizon Suite.  I expected this exam to be slightly more difficult than the VCA-DCV exam but a little easier than the VCA-Cloud exam based on my overall experience with all technologies involved.  Basically, knowledge is needed about each of the features in the Horizon Suite and what is appropriate and where from a product/solution positioning standpoint.  In a word, this exam was frustrating.  I felt good about all of the straight forward questions addressing features and functionality and plowed through those quickly.  However, I encountered about a dozen questions of a particular style in which I wasn’t quite sure what was being asked based on the answers provided.  Without explicitly divulging test questions, the ask was to identify an infrastructure or business challenge that would need to be addressed in order to deploy a given VMware Horizon Suite solution.  That is the way each of the questions of this style was worded.  While that is all well and good, the answers provided seem to discuss areas that the resulting Horizon deployment would implicitly address, rather than areas that needed to be addressed prior to a deployment – and in many cases, each of the provided answers were correct to a degree.  For each, I chose the closest answer but again I didn’t feel any of the answers fit the wording of the question being asked.  I left comments on each of the questions I felt weren’t clear and I also grabbed screenshots of each of these questions which I may reference should VMware wish to contact me regarding my comments.

The laptop I was taking the exam suffered an Internet Explorer crash four times and I had to resume the exam each of the four times.  The test engine appeared to handle these scenarios well.

 

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Now… I will move on to the VCAP5-DCA which I’ve been blowing off successfully since its launch.  That exam is scheduled for early November (earliest available slot at my nearby exam centers) with a 70% off voucher, again thanks to my friends on Twitter.

VCA-Cloud Exam Review

October 14th, 2013

Following up on my last post on the VCA-DCV Exam Review and in identical style, Friday evening I sat the VMware Certified Associate – Cloud (VCA-Cloud) exam (exam code VCAC510).

VMware’s take on VCA-Cloud preparation:

There is no training requirement, however there is a free, self-paced elearning class that can help you prepare.

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VMware summarizes the VCA-Cloud certification as follows:

With the VCA-Cloud certification, you’ll have greater credibility when discussing cloud computing, the business challenges the vCloud Suite is designed to address, and how deploying the vCloud solution addresses those challenges. You’ll be able to define cloud computing and provide use case scenarios of how vCloud and cloud computing can take advantage of private and public clouds without changing existing applications and leverage a common management, orchestration, networking, and security model.

VMware further explains that a successful candidate who passes the VCA-Cloud will realize the following benefits:

  • Recognition of your technical knowledge
  • Official transcripts
  • Use of VCA-Cloud logo
  • Access to the exclusive VCA portal & logo merchandise store
  • Invitation to beta exams and classes
  • Discounted admission to VMware events
  • Greater opportunities for career advancement

Once again, I recognize two additional benefits to this exam experience:

  • The exam can be taken online from any location with a compatible internet web browser and an internet connection
  • By virtue of the above, coffee is available in the exam room – those who know me know this is a perk

Chris Wahl has a new blog post introducing The New VMware Certified Associate (VCA) Exams.  His video includes VCA exam background, preparation, as well as step by step instructions covering exam registration.

On to the exam.  Length for native English speaking vGeeks is 50 questions in 75 minutes.  Both multiple choice and multiple select style of questions.  VMware’s exam summary was consistent with my exam experience.  I’d also add that there was a pretty large focus on hybrid cloud solutions and connectivity.  I found this exam to be more difficult and outside the scope of my daily expertise than the VCA-DCV exam.  While I’ve had quite a bit of experience with vCloud Director and its operational use of storage and networking, and those discussion points weren’t much of a problem, I was at a clear disadvantage in areas covering vFabric Suite, Hyperic, and slightly deeper use of vCOPS.  All of these topics garnered significant focus making it clear that VMware is making a very strong and intentional push into the private/hybrid/public cloud spaces.

I took my time on this exam and did not provide any comments/feedback as I did on the VCA-DCV exam.  At one point I had to stop because lightning, thunder, and rain rolled up on the deck attached to the back of my house where I was taking the exam.  I had to take my laptop, coffee, and cigar to the front of the house which is covered by the stoop.  If the candidate has a basic understanding of VMware’s product portfolio as well as the fundamental features in vSphere, time management shouldn’t be an issue.

I was able to pass the exam adding VCA-Cloud to my suite of certifications.

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I will now move on to the VCAP5-DCA which I’ve been blowing off successfully since its launch.  That exam is scheduled for early November (earliest available slot at my nearby exam centers) with a 70% off voucher, again thanks to my friends on Twitter.  In the interim, I may also take a look at the VMware Certified Associate – Workforce Mobility (VCA-WM) exam.

VCA-DCV Exam Review

October 11th, 2013

Last week I saw a tweet referring to a link to the Perfect Cloud virtualization blog which contained a free voucher for the VMware Certified Associate – Data Center Virtualization (VCA-DCV) exam (exam code VCAD510).  Admittedly, in the past I didn’t have much interest in sitting this exam but with the free voucher available, I thought I’d give it an impromptu shot (translated: I’ll be sitting the exam immediately with no preparation. Many test takers refer to this as ‘going in cold‘).  My reasoning was that having sat advanced level VMware certifications in the past, I wasn’t overly concerned with preparation on this one.

VMware’s take on VCA-DCV preparation:

There is no training requirement, however there is a free, self-paced elearning class that can help you prepare.

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VMware summarizes the VCA-DCV certification as follows:

With the VCA-Data Center Virtualization certification, you’ll have greater credibility when discussing data center virtualization, the business challenges that vSphere is designed to address, and how virtualizing the data center with vSphere addresses those challenges. You’ll be able to define data center virtualization and provide use case scenarios of how vSphere and data center virtualization can provide cost and operational benefits.

VMware further explains that a successful candidate who passes the VCA-DCV will realize the following benefits:

  • Recognition of your technical knowledge
  • Official transcripts
  • Use of VCA-DCV logo
  • Access to the exclusive VCA portal & logo merchandise store
  • Invitation to beta exams and classes
  • Discounted admission to VMware events
  • Greater opportunities for career advancement

Personally, I would add two additional benefits to this exam:

  • The exam can be taken online from any location with a compatible internet web browser and an internet connection
  • By virtue of the above, coffee is available in the exam room – those who know me know this is a perk

Chris Wahl has a new blog post introducing The New VMware Certified Associate (VCA) Exams.  His video includes VCA exam background, preparation, as well as step by step instructions covering exam registration.

On to the exam.  Length for native English speaking vGeeks is 50 questions in 75 minutes.  Both multiple choice and multiple select style of questions.  VMware’s exam summary was spot on, at least for the latter parts (I’m still awaiting peer/industry feedback on the increase of my credibility part).  Most of the questions dealt with a variably complex business need revolving around… yep you guessed it – datacenter virtualization, and the requirement to recommend a corresponding VMware product or feature that meets the customer need.  Most of the Q & A was straightforward but there were a few I came across which either the question or answers provided were vague enough such that the resulting answer will be left to interpretation leading either to a correct or incorrect answer.  Having plenty of time to complete the exam, I left comments/feedback on these items.

I completed the exam in 20 minutes including the comments/feedback on a handful of questions.  If the candidate has a basic understanding of VMware’s product portfolio as well as the fundamental features in vSphere, time management shouldn’t be an issue.

And that wraps it up.  I’ve added VCA-DCV to my suite of certifications.

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I will now move on to the VCAP5-DCA which I’ve been blowing off successfully since its launch.  That exam is scheduled for early November (earliest available slot at my nearby exam centers) with a 70% off voucher, again thanks to my friends on Twitter.

vSphere 5.5 UNMAP Deep Dive

September 13th, 2013

One of the features that has been updated in vSphere 5.5 is UNMAP which is one of two sub-components of what I’ll call the fourth block storage based thin provisioning VAAI primitive (the other sub-component is thin provisioning stun).  I’ve already written about UNMAP a few times in the past.  It was first introduced in vSphere 5.0 two years ago.  A few months later the feature was essentially recalled by VMware.  After it was re-released by VMware in 5.0 Update 1, I wrote about its use here and followed up with a short piece about the .vmfsBalloon file here.

For those unfamiliar, UNMAP is a space reclamation mechanism used to return blocks of storage back to the array after data which was once occupying those blocks has been moved or deleted.  The common use cases are deleting a VM from a datastore, Storage vMotion of a VM from a datastore, or consolidating/closing vSphere snapshots on a datastore.  All of these operations, in the end, involve deleting data from pinned blocks/pages on a volume.  Without UNMAP, these pages, albeit empty and available for future use by vSphere and its guests only, remain pinned to the volume/LUN backing the vSphere datastore.  The pages are never returned back to the array for use with another LUN or another storage host.  Notice I did not mention shrinking a virtual disk or a datastore – neither of those operations are supported by VMware.  I also did not mention the use case of deleting data from inside a virtual machine – while that is not supported, I believe there is a VMware fling for experimental use.  In summary, UNMAP extends the usefulness of thin provisioning at the array level by maintaining storage efficiency throughout the life cycle of the vSphere environment and the array which supports the UNMAP VAAI primitive.

On the Tuesday during VMworld, Cormac Hogan launched his blog post introducing new and updated storage related features in vSphere 5.5.  One of those features he summarized was UNMAP.  If you haven’t read his blog, I’d definitely recommend taking a look – particularly if you’re involved with vSphere storage.  I’m going to explore UNMAP in a little more detail.

The most obvious change to point out is the command line itself used to initiate the UNMAP process.  In previous versions of vSphere, the command issued on the vSphere host was:

vmkfstools -y x (where x represent the % of storage to unmap)

As Cormac points out, UNMAP has been moved to esxcli namespace in vSphere 5.5 (think remote scripting opportunities after XYZ process) where the basic command syntax is now:

esxcli storage vmfs unmap

In addition to the above, there are also three switches available for use; of first two listed below, one is required, and the third is optional.

-l|–volume-label=<str> The label of the VMFS volume to unmap the free blocks.

-u|–volume-uuid=<str> The uuid of the VMFS volume to unmap the free blocks.

-n|–reclaim-unit=<long> Number of VMFS blocks that should be unmapped per iteration.

Previously with vmkfstools, we’d change to VMFS folder in which we were going to UNMAP blocks from.  In vSphere 5.5, the esxcli command can be run from anywhere so specifying the the datastore name or the uuid is one of the required parameters for obvious reasons.  So using the datastore name, the new UNMAP command in vSphere 5.5 is going to look like this:

esxcli storage vmfs unmap -l 1tb_55ds

As for the optional parameter, the UNMAP command is an iterative process which continues through numerous cycles until complete.  The reclaim unit parameter specifies the quantity of blocks to unmap per each iteration of the UNMAP process.  In previous versions of vSphere, VMFS-3 datastores could have block sizes of 1, 2, 4, or 8MB.  While upgrading a VMFS-3 datastore to VMFS-5 will maintain these block sizes, executing an UNMAP operation on a native net-new VMFS-5 datastore results in working with a 1MB block size only.  Therefore, if a reclaim unit value of 100 is specified on a VMFS-5 datastore with a 1MB block size, then 100MB data will be returned to the available raw storage pool per iteration until all blocks marked available for UNAMP are returned.  Using a value of 100, the UNMAP command looks like this:

esxcli storage vmfs unmap -l 1tb_55ds -n 100

If the reclaim unit value is unspecified when issuing the UNMAP command, the default reclaim unit value is 200, resulting in 200MB of data returned to the available raw storage pool per iteration assuming a 1MB block size datastore.

One additional piece to to note on the CLI topic is that in a release candidate build I was working with, while the old vmkfstools -y command is deprecated, it appears to still exist but with newer vSphere 5.5 functionality published in the –help section:

vmkfstools vmfsPath -y –reclaimBlocks vmfsPath [–reclaimBlocksUnit #blocks]

The next change involves the hidden temporary balloon file (refer to my link at the top if you’d like more information about the balloon file but basically it’s a mechanism used to guarantee blocks targeted for UNMAP are not in the interim written to by an outside I/O request until the UNMAP process is complete).  It is no longer named .vmfsBalloon.  The new name is .asyncUnmapFile as shown below.

/vmfs/volumes/5232dd00-0882a1e4-e918-0025b3abd8e0 # ls -l -h -A
total 998408
-r——–    1 root     root      200.0M Sep 13 10:48 .asyncUnmapFile
-r——–    1 root     root        5.2M Sep 13 09:38 .fbb.sf
-r——–    1 root     root      254.7M Sep 13 09:38 .fdc.sf
-r——–    1 root     root        1.1M Sep 13 09:38 .pb2.sf
-r——–    1 root     root      256.0M Sep 13 09:38 .pbc.sf
-r——–    1 root     root      250.6M Sep 13 09:38 .sbc.sf
drwx——    1 root     root         280 Sep 13 09:38 .sdd.sf
drwx——    1 root     root         420 Sep 13 09:42 .vSphere-HA
-r——–    1 root     root        4.0M Sep 13 09:38 .vh.sf
/vmfs/volumes/5232dd00-0882a1e4-e918-0025b3abd8e0 #

As discussed in the previous section, use of the UNMAP command now specifies the the actual size of the temporary file instead of the temporary file size being determined by a percentage of space to return to the raw storage pool.  This is an improvement in part because it helps avoid the catastrophe if UNMAP tried to remove 2TB+ in a single operation (discussed here).

VMware has also enhanced the functionality of the temporary file.  A new kernel interface in ESXi 5.5 allows the user to ask for blocks beyond a a specified block address in the VMFS file system.  This ensures that the blocks allocated to the temporary file were never allocated to the temporary file previously.  The benefit realized in the end is that any size temporary file can be created and with UNMAP issued to the blocks allocated to the temporary file, we can rest assured that we can issue UNMAP on all free blocks on the datastore.

Going a bit deeper and adding to the efficiency, VMware has also enhanced UNMAP to support multiple block descriptors.  Compared to vSphere 5.1 which issued just one block descriptor per UNMAP command, vSphere 5.5 now issues up to 100 block descriptors depending on the storage array (these identifying capabilities are specified internally in the Block Limits VPD (B0) page).

A look at the asynchronous and iterative vSphere 5.5 UNMAP logical process:

  1. User or script issues esxcli UNMAP command
  2. Does the array support VAAI UNMAP?  yes=3, no=end
  3. Create .asyncUnmapFile on root of datastore
  4. .asyncUnmapFile created and locked? yes=5, no=end
  5. Issue 10CTL to allocate reclaim-unit blocks of storage on the volume past the previously allocated block offset
  6. Did the previous block allocation succeed? yes=7, no=remove lock file and retry step 6
  7. Issue UNMAP on all blocks allocated above in step 5
  8. Remove the lock file
  9. Did we reach the end of the datastore? yes=end, no=3

From a performance perspective, executing the UNMAP command in my vSphere 5.5 RC lab showed peak write I/O of around 1,200MB/s with an average of around 200IOPS comprised of a 50/50 mix of read/write.  The UNMAP I/O pattern is a bit hard to gauge because with the asynchronous iterative process, it seemed to do a bunch of work, rest, do more work, rest, and so on.  Sorry no screenshots because flickr.com is currently down.  Perhaps the most notable takeaway from the performance section is that as of vSphere 5.5, VMware is lifting the recommendation of only running UNMAP during a maintenance window.  Keep in mind this is just a recommendation.  I encourage vSphere 5.5 customers to test UNMAP in their lab first using various reclaim unit sizes.  While do this, examine performance impacts to the storage fabric, the storage array (look at both front end and back end), as well as other applications sharing the array.  Remember that fundamentally the UNMAP command is only going to provide a benefit AFTER its associated use cases have occurred (mentioned at the top of the article).  Running UNMAP on a volume which has no pages to be returned will be a waste of effort.  Once you’ve become comfortable with using UNMAP and understanding its impacts in your environment, consider running it on a recurring schedule – perhaps weekly.  It really depends on how much the use cases apply to your environment.  Many vSphere backup solutions leverage vSphere snapshots which is one of the use cases.  Although it could be said there are large gains to be made with UNMAP in this case, keep in mind backups run regularly and and space that is returned to raw storage with UNMAP will likely be consumed again in the following backup cycle where vSphere snapshots are created once again.

To wrap this up, customers who have block arrays supporting the thin provision VAAI primitive will be able to use UNMAP in vSphere 5.5 environments (for storage vendors, both sub-components are required to certify for the primitive as a whole on the HCL).  This includes Dell Compellent customers with current version of Storage Center firmware.  Customers who use array based snapshots with extended retention periods should keep in mind that while UNMAP will work against active blocks, it may not work with blocks maintained in a snapshot.  This is to honor the snapshot based data protection retention.

Did You <3 VMware at VMworld?

September 2nd, 2013

This large whiteboard was made available for VMworld 2013 attendees in the back of the VMware booth.  The photo was taken on Monday afternoon.

Click on the image for a larger version.

Did you <3 VMware and tell them why?  Show other readers where you signed in the comments section below.

Can you accurately identify where I signed?  If so, send an email to jason@boche.net with the subject Mastering vSphere 5.5 Book.  The first five correct answers will receive a paperback copy of the new Mastering VMware vSphere 5.5 book by authors Scott Lowe, Nick Marshall, Forbes Guthrie, Matt Liebowitz, and Josh Atwell.  Availability of the book is late October or early November according to Scott Lowe.

 

telluswhyyoulovevmware

Update 11/1/13:  The winners have been announced in this blog post.  Thank you to all who participated!