1 2 Previous Next 29 Replies Latest reply on Oct 31, 2014 5:58 PM by TheVMinator Go to original post
      • 15. Re: Disk Alignment on guest VM's
        mcowger Champion

        MOST array vendors (including NetApp and EMC) don't recommend defrag, because it moves data around the array uncessarily, with no benefit, and can even harm the automatic tiering algorithms.

        • 16. Re: Disk Alignment on guest VM's
          meistermn Master

          Why aren't there partitioning tools on the market ?




          The task of migrating the operating system, applications and files from one storage drive to another can be a slow and tedious process. Paragon Migrate OS to SSD 2.0 simplifies the migration process by providing an intuitive wizard-driven interface. Paragon Migrate OS to SSD automatically downsizes the source system volume, if needed; auto-aligns the copied system partition; and provides intelligent selection of specific files and folders for migration — all without rebooting the system.


          I do not understand the last part: all without rebooting the system.  Does this mean online realignment from hard disk to ssd. If so why not from vharddisk to vhardisk?

          • 17. Re: Disk Alignment on guest VM's
            Lessi001 Enthusiast



            just my 2 cents...


            We have the same situation - a lot of 2003 Servers which are misaligned...


            As maintenance windows are rare using an alignment technology which leads to offline times was not suitable for us.

            So we decided to use the NetApp VSC 4  Optimization and Migration Tool.


            As "meistermn" wrote this is not a real alignment. How it works you can read here if you want (Part 3):



            We have aligned about 50 misaligned VMs in about 8 hours work - without any interruption of our production.


            Unfortunately we do not see any improvement of performance from our storage till now...




            • 18. Re: Disk Alignment on guest VM's
              jdptechnc Expert

              meistermn wrote:


              okay it was some ago I tried with vconverter 5.0 beta , so it seems still no change. Maybe in the next verson of converter.


              You have to explicitly use the "select volumes to copy" option in order to expose the option to optimize layout.


              We are on NetApp and saw the feature in VSC to create the offset datastore in order to align the I/O and not sustain downtime, but in the end, we decided against that.  It would tie those VM's to this special purpose datastore forever (and create a datastore that no properly aligned VM should use), and it doesn't really solve the problem.


              I didn't like mbralign either, because it only aligned the VM at 32K, which is OK for netapp, but if we move these VMs to other vendor storage, 64K at least seems be the recommendation.

              • 19. Re: Disk Alignment on guest VM's
                RParker Guru

                Very basic simple answer, as I said..this topic isn't new, it has been discussed, heated arguments.. for against, no one every wins.. but I will try to break it down.


                WAFL is a block.  The VM resides as a block of data... It's no smaller than 4K.. there *ARE* Windows NTFS blocks within that block of data on the SAN.  *THAT's* what we are defragging.. not the SAN.


                So Defrag WILL benefit.. Execsoft has proven it, and Netapp depending on the engineer, they agree or disagree depending on mood.  Even Netapp cannot get an agreement as a company.


                Defrag ONLY runs when needed.. if your blocks are up to date, no need to KEEP defragging.  The more often you defrag, the less time it takes.  Perfect disk talks to vCenter to ensure that a moderate of VM's are running concurrently and it will not overrun the SAN (this can be adjusted).


                So a block may be optimized on the SAN but it's not optimized within the Guest OS File system level.. that's what we are defragging.. FILES not blocks.  For every IOP that is required from Windows less on the SAN, saves more IOPS for the SAN.  So that's my take on defrag.. we are simply making files within the guest more efficient, and therefore less reads.


                It's PROVEN benefit, regardless of what your netapp tech says.  I can find a Netapp tech that will disagree with HIM (or her).

                • 20. Re: Disk Alignment on guest VM's
                  RParker Guru

                  meistermn wrote:


                  Why aren't there partitioning tools on the market ?


                  I do not understand the last part: all without rebooting the system.  Does this mean online realignment from hard disk to ssd. If so why not from vharddisk to vhardisk?

                  You are aligning the VM disk TO the SAN.  IT's a starting block, so they all have the same start / end points.  If you start at 100 and I start at 99 and our blocks are the same size (10 blocks lets say).


                  1 for block of data starting at 99 and one more for the 9 remaining blocks starting at 100. I will require 2 reads to your 1.  You are more efficient.  If I align my blocks to yours, we start / stop at the same point.  Thereby aligned and no overlap.


                  That's a very simplistic answer.. but that's how it works basically.  All we are doing is making everyone start at the same place... and since blocks of data is all the same (4K) cluster size, thus we can be in sync.

                  • 21. Re: Disk Alignment on guest VM's
                    RParker Guru

                    Matt wrote:


                    MOST array vendors (including NetApp and EMC) don't recommend defrag, because it moves data around the array uncessarily, with no benefit, and can even harm the automatic tiering algorithms.

                    Which is largely untrue.. we are NOT moving blocks around the SAN, we are simply defragging FILES *WITHIN* those same blocks... That's where everyone goes off the reservation... Defrag is at the GUEST OS level not SAN level... WAFL can still maintain the blocks ON the SAN, the files within the GUEST OS file system are *NOT* managed by the SAN, and therefore not part of the WAFL optimization..


                    The NTFS STILL needs to be defragged within a given block.  That's ALL we are doing.  Also automatic tiering is done over time (averaged).. so it's not going to affect anything.  Even if it does move SOME data.. ONLY the blocks that have higher IOPS get moved.. not ALL the blocks. so it's a very minor change.. in reality that's why we using the tiering method, get the higher performing IOPS OFF the lower performing spindles.. that's what's its for.  Once the IOPS return to normal those blocks will be moved back... once they are defragged, we don't need to KEEP defragging.  Start only when needed.

                    • 22. Re: Disk Alignment on guest VM's
                      jdptechnc Expert

                      I think EMC, NetApp, etc, do not come out in favor of recommending defrag to the general population because most lay-admins are just going to click-click-next and not consider the downstream ramifications of what they are doing (thinly provisioned disks being allocated more space unexpectely due to data being moved to previously unused blocks, blocks becoming hot and moving up a tier, or whatever).  It's easier for the vendor to just say not to do it unless you really know what you are doing.

                      • 23. Re: Disk Alignment on guest VM's
                        mcowger Champion

                        You may believe your theories.  They aren't reality, but enjoy them.


                        Nonetheless, neither EMC nor NetApp recommend it.    Is it possible they know more about the impact of defrag on their arrays than you do?  Just possible?

                        • 24. Re: Disk Alignment on guest VM's
                          cdnls Lurker

                          Hi There


                          For anyone attempting this.

                          We used a combination of EBRALIGN, MBRALIGN and robocopy!

                          850 VMs (Linux and Windows) .

                          Change Management followed to the letter (god that was hard)
                          Started in June...finished in November!

                          The over time bill was massive!

                          • 26. Re: Disk Alignment on guest VM's
                            markzz Enthusiast

                            There is a commercial tool available to complete disk alignments for you. The product was a written by vizioncore it's called vOptimizer.
                            This product is intended to perform many disk optimisation tasks in the virtual environment, one of these is start sector alignment, in fact it's the only feature I have ever used..
                            I have not used the product for over a year now.. Seems when vizioncore were purchased by Quest they went from being a friendly flexible company to a difficult, rigid and unresponsive one.
                            I've been reading this post in preparation for checking the alignment of our guest disks, we have completed a SAN migration and I feel the command latencies are higher than I'd expect..I therefore suspect during migration there may have been misalignment introduced into what was an optimised environment..
                            I'm dreading having to deal with Quest support..eg. I know we paid our maintenance on vOptimiser but as expected there was never a new license file sent for the new version.. I'm sure I can blow a couple of hours with support on this alone..
                            I'd hoped there was another product available which could perform disk alignments in a managed GUI interface..I've not found any yet beyond vOptimizer.


                            I see Quest has been bought by Dell.. hmmm they couldn't do any worse.

                            • 27. Re: Disk Alignment on guest VM's
                              JoelH Novice

                              Hello Matt,


                              I'm having a hard time getting copy of UberAlign. The download link for the OVA at nickopedia.com doesn't work. Do you know of a working download location?


                              Thank you,



                              • 28. Re: Disk Alignment on guest VM's
                                mcowger Champion

                                You'd have to ping Nick(@lynxbat on twitter) - it was his tool.  He doesn't work for EMC anymore (moved on to Intel)....

                                • 29. Re: Disk Alignment on guest VM's
                                  TheVMinator Master

                                  Regarding NetApp, this document may clarify, though it is out of date an has not been updated since vSphere 4.x:




                                  I would like to know if there is more current information or official documentation from them. Different technicians that come into NetApp start with as varied of backgrounds as those commenting in this post, and may have express opinions  differing from each other [disclosure - I used to be one back during the time this was current] , but before something gets published as this paper, it gets more of an official approval process.


                                  Important I think in this document is this concept, that with VMFS there are two layers, not one layer of alignment:

                                  1. The layer between the guest file system and VMFS, and

                                  2. the layer between VMFS and the Array (not as much of an issue in newer VMFS versions)


                                  Any thoughts on this paper?

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