VMtoday

I’ve held off on posting this as I don’t like to toot my own vuvuzela too loudly, but in a fit of shameless self promotion and a desire to see the program grow, here goes nothin:

I am a VMware vExpert!

VMware notifed recipients of the designation last month.  The 300 or so awardees are recognized for their “advocacy of VMware solutions, your contributions to the community of VMware users, and your willingness to share your expertise with others.”  I find it an absolute honor to be included amongst the vExpert class of 2010 – a group full of folks who are on the cutting edge of virtualization and cloud computing, many of whom have helped me through their books, blogs, and contributions to the VMware Community.  Arnim van Lieshout has compiled a nice list of vExperts here: http://www.van-lieshout.com/vexpert-2010/.

It’s an exciting time to be a virtualization professional – in terms of the technology, people and seemingly endless opportunities.  I look forward to continuing my contributions to the community through this here blog, my leadership of the Washington, DC Metro Area VMware User Group, and through my work as a implementer of VMware solutions!  Special thanks to John Troyer for sponsoring the program and doing so much to organize the VMware community through the weekly VMware Community Roundtable, Social Media and the many other programs he touches.

I upgraded my in-house VMware vSphere environment to 4.0 Update 2 last week.  After upgrading my vSphere Client to the Update 2 version I was greeted with a series of 7 ugly error messages stating: Method not found: ‘VMware.CustomControls.LabelEx VpxClient.Common.Util.Helper.AddLabel(System.Windows.Froms.Control,Int32, int32, System.String, System.Drawing.FontStyle, Boolean)”.I assumed a plug-in had caused the error message.  I started my troubleshooting by disabling the 3rd-party plug-ins in the environment, beginning with the free EMC Storage Viewer.  Upon disabling the EMC Storage Viewer 2.x plug-in the problem was resolved.  I went out to EMC PowerLink to see if an update was available for the plug-in and was surprised to find that I had missed a major update/rebranding of the plug-in.  EMC now calls the plug-in the ‘EMC Virtual Storage Integrator’.  A hotfix was released on July 2nd to bring Update 2 support to the plug-in (version 3.0.0.32).

I updated the Solution Enabler installation (I installed Solution Enabler on my vCenter server, but it is also available as a SUSE based virtual appliance), and then updated the plug-in.

The update appeared to install without any problems.  The vSphere Client launched like a champ after the update – no errors, but no EMC Storage plug-in either.  Odd.  The problem occurred on both my vCenter Server’s vSphere client and my workstation, so seems to be more than an isolated issue.

I did an uninstall of the plug-in using Add/Remove Programs, and then reinstalled it.  After the reinstall the EMC Storage plug-in icon appeared in my vSphere Client as pictured below.

The EMC Virtual Storage Integrator (VSI) plug-in is free – installing it is a no-brainer for anyone running Clariion or Celerra storage arrays.  The VSI simplifies the job of mapping vSphere Datastores to LUN’s and NFS shares on your EMC storage, and helps pinpoint the location of VM’s and RDM’s on your array.  This visibility for the VMware administrator into the storage layer can go a long way in helping troubleshoot storage performance issues and simplifying communication between server, storage, and virtulization teams.

EMC actually offers three different free vSphere plug-ins, including the VSI.  The EMC Unified Block plug-in and the EMC Unified NAS plug-in round out the trio.  EMC’s Virtual Geek, Chad Sakac, covers all three in his blog post here: http://virtualgeek.typepad.com/virtual_geek/2010/06/update-on-emc-vsphere-plugins.html.

At the risk of beating a dead horse, it’s time to resurrect my Storage Basics series.  I’ve recently had some great feedback on the series and figured I should round out a few of the concepts before I wrap it up.  I want to cover a topic often discussed amongst virtualization professionals, but one I often find general practitioners and server admins not understanding: storage alignment.  Storage alignment, or the lack of alignment, is not a new issue and is not unique to VMware or virtualization in general.  However, the effects of misaligned storage can be more greatly felt in terms of reduced performance and strain on a storage system in shared, oversubscribed or high I/O environments.  Many others in the virtualization and storage communities have already covered partition alignment (see Duncan Epping, Vaughn Stewart, and most recently Chad Sakac), but I feel it is an important enough topic for me to re-hash as part of this series.

What is Storage Alignment?

Let’s start with a quick overview of what storage alignment means.  Quite simply, storage alignment refers to the positioning (starting offset) of the various pieces of a systems storage components – the physical disk sectors or array’s chunks, the VMware File System (VMFS) in a VMware environment, and the guest file system’s clusters within a partition – in relation to the layer directly under the element in question.  A quick graphic often makes quick work of explaining this (I often whiteboard this concept for colleagues and clients):

As you can see, the starting offset of the VMFS partition does not correspond to the physical segmentation of the underlying disks (in this case, the chunks on a SAN – but could be conceptually replaced with the sectors of a single disk).  Furthermore, the clusters (or blocks) of the guest VM are not aligned to the VMFS partition nor to the underlying storage.  For traditional (physical) systems or VMware RDM’s, the VMFS layer could be abstracted, but the result would be the same – the clusters of a partition would be misaligned to the underlying disk.

What Does it Mean?

Quite simply, misaligned storage (both VMFS partitions and Guest File Systems) can lead to poor performance under certain conditions.  How badly performance is impacted depends on the degree of I/O strain your server and storage are under, the caching mechanisms in your environment, and the architecture of your SAN.  Again, a visual can help explain how misaligned storage can hurt you. For simplicity let’s leave out the VMFS layer as we consider the following diagram (pardon my hasty Visio visualization):

What we see is that the target data in a tiny 16kb read request spans two 64kb chunks on our storage array.  Any reads of that piece of data will result in twice the amount of data as would be minimally necessary being transferred to the host’s storage stack.  The net effect is an increase in the work the storage array must do – gobbling up IOPS that would otherwise be available for the real work of reading data, reducing throughput on the interface, and messing with cache algorithms and dedupe mechanisms on some arrays.  In short, misaligned storage is an efficiency killer.  Now add in the VMFS layer back in and you’ll see how things get complicated.

If (and we’re talking a big IF here) every bit of data you wanted to read spanned a chunk or sector boundary, you could experience half the expected performance due to misalignment.  In reality, depending on your workload and storage technology your performance increase from properly aligning your storage will probably be somewhere between 10-30%.

Want to dig deeper?

There have been some great resources published on this issue over the past few years on storage alignment.  Major vendors have all begun pushing information on the problem – here are some of the best that I have found:

Microsoft has a Knowledge Base article (http://support.microsoft.com/kb/929491) that describes the problem and symptoms of misaligned partitions, how to determine if your partition is aligned, and the use of diskpart to create aligned partitions.

Microsoft also has an in-depth article on MSDN, including some performance numbers at http://msdn.microsoft.com/en-us/library/dd758814.aspx.  Also check out Jimmy May’s series Partition (Sector) alignment for SQL Server here: http://blogs.msdn.com/b/jimmymay/archive/2008/10/14/disk-partition-alignment-for-sql-server-slide-deck.aspx.  One of the best descriptions of the complexities of the problem can be found in Jimmy’s blog series.

VMware has an article here: http://www.vmware.com/pdf/esx3_partition_align.pdf.  Be aware that this article is for Virtual Infrastructure 3, not vSphere 4.0.  Some of the information is now a bit dated.

Netapp has a few documents to check out: http://media.netapp.com/documents/tr-3428.pdf (VI3), and http://media.netapp.com/documents/tr-3749.pdf (vSphere)

EMC covers alignment in their TechBooks for Clariion, Celerra, and Symmetrix.

Tools to Align Partitions:

Ok – so you’ve bought into this whole partition alignment thing as being a real issue.  How to you fix it?  Here are some tools:

1. MSInfo32.exe, wmic, and dmdiag will show you misaligned partitions on Windows machines (check the Microsoft links above for usage info).
2. Diskpart.exe (or diskpar.exe on versions of Windows previous to 2003) creates aligned partitions on Windows systems.  Diskpart cannot be used to realign a previously created partition, only to create new correctly aligned partitions.
3. MBRScan/MBRAlign from NetApp can report on and realign existing virtual disks on a VMware ESX server.  Also a nifty PowerShell script from NetApp to find if your partitions are aligned: http://communities.netapp.com/docs/DOC-6175
4. vOptimizer from Vizioncore can report on and realign existing virtual disks.
5. GParted can be used to create aligned partitions on both Windows and Linux machines, and to realign some existing partitions.
6. VMware vCenter – VMFS datastores created using vCenter are aligned automatically. Note – Guest VMDK’s are not aligned automatically by vCenter – you must manually create aligned partitions on your VMDK’s or use a Guest OS that creates properly aligned partitions (Windows 2008 and later).

Best Practices:

Before I wrap this installment up, here are some best practices for storage alignment in your environment:

• Create aligned partitions in your VMware templates. Do it once, do it right – every machine you deploy from the template will be aligned.
• Use caution with tools like Symantec Ghost.  Ghost can take images of aligned partitions and misalign them when laying down on a new system.
• Use caution when performing P2V’s using VMware vCenter Converter – it does not align guest disks on import.  You might consider using Converter to perform a P2V of the system disk only, then create new VMDK’s on the converted guest.  Use Diskpart, gparted, or another tool to create aligned partitions on the new VMDK’s and finally copy the data over to the newly virtualized server using a tool like Robocopy, RichCopy, or rsync.
• SSD’s are particularly sensitive to misalignment, leading to poor performance and excessive wear.
• Local VMFS volumes created by the ESX installer are not aligned.  If you are using an installer-created local VMFS for anything where performance matters, you might consider re-creating it through vCenter.
• Watch out when attaching a data disk from an older VM to a new VM.  For example, you are upgrading your SQL servers to Windows 2008 R2 from 2003.  You decide to do a side-by-side upgrade, using the detach/attach method.  You install (or better yet, deploy from template) a new Windows 2008 R2 VM, detach your databases from the old server, move your SQL data and log virtual disks from your 2003 VM to the new VM and attach the SQL DB’s on the new server.  Those old VMDK’s may be misaligned!  Consider using Robocopy, RichCopy or rsync to ensure an aligned disk.
• Check your storage vendors best practices for your particular environment (OS, workload, SAN, etc.).
• There is some debate on whether or not it is advised to align your OS partitions.  There is no clear-cut answer on this as it depends so much on your environment and particular needs.  For help in deciding if you should align your Guest OS drives, see the comments in the blogs by Duncan Epping, Vaughn Stewart, and Chad Sakac.
• While working the VMware User Group booth at the Washington, DC Virtualization Forum 2010 I had a user ask me if rules and procedures for alignment on 4k sector disks are different. I forgot to research it until just now, so I honestly don’t know (please comment if you do know!).  Check with your storage vendor if this is an issue for you.
• Finally, you can’t realign partitions using tools like mbralign or vOptimizer in ESXi -Aaaron Delp explains the problem here: http://blog.aarondelp.com/2010/06/my-1-issue-with-vmware-esxi-today.html.

I hope this is helpful for you in understanding the problem of storage alignment and how it can impact your environment.  Comments or questions are welcomed!

One of my most popular posts to date had been IBM DS3300 Write Performance Problem Solved.  I am pleased to have upgrade my internal environment to an EMC Clariion CX4 array, but still have customers using the DS3300 and the MD3000i from Dell.  For that reason, I keep an eye out for news on these arrays.  You’ll recall that these arrays are based on the same LSI kit.  Truth be told, properly designed and configured, these arrays are a technically proficient and cost efficient solution for SMB’s looking to get their VMware environments going.

While reviewing my email today I found an email from SolarWinds about their new Free SAN Monitor.  I have used several products from SolarWinds in the past, and so thought I would give this a quick try.  This tool can monitor the LSI-based arrays from Dell (including the MD3000 series), IBM (DS3000, DS4000, and DS5000), and SunStorageTek 2000 and 60000.  Installation and configuration were both fast and easy.  A wizard asked me for the array’s IP address, monitoring interval, and some thresholds (which I left blank).  Once I clicked Finish the app launched on my desktop and immediately began to display data.

This screen-shot is of the app running on my Windows 7 x64 workstation.  You’ll notice that the array is reporting performance, in terms of IOPS, and response time for individual LUNS.  The health of my array is also displayed.  You’ll see that my ‘Controller 2′ shows a failure.  I do not have a dual-controller configuration (hence my wildly popular post on performance being in the tank due to a disabled write cache).  The SAN Monitor incorrectly reported that I had two controllers, and that the 2nd is failed.

This is not bad for a free tool, in my opinion.  I would love to see SolarWinds add some info on write cache status for the array (cache hit %, cache enabled per LUN, etc.) as well as LUN utilization in terms of free space remaining.  For a free desktop GUI, it’s worth the 5 minutes to download and setup.

Reporting on I/O Response time (in milliseconds) is helpful in determining if your array is stressed.  If response times are consistently above 15ms, you ought to look at adding some spindles.  If you are over 25ms on a regluar basis, you’re likely feeling some pain on the servers generating the workload against your array.

If you are into the whole free tool thing, SolarWinds also has a free VM Monitor that is capable of monitoring a single ESX server via SNMP and it’s associated VM’s.  It too runs as a desktop application, requiring minimal setup and configuration.  While it won’t monitoring your whole VMware Essentials (3 ESX servers + vCenter) environment, it’s a start.

You might also check out Nick Weaver’s vSphere Mini Monitor for basic real-time alerts and monitors, as well as NetWrix’s Change Reporter for VMware.  A final free (and nothing short of awesome) tool is Alan Renouf’s vCheck Daily Report PowerShell Script.

Do you have free tools, scripts or utilities for your VMware environment?  I’d love to hear more about them in the comments section!