6 Replies Latest reply: Oct 17, 2013 10:10 AM by Alan Rutledge RSS

    Question on nimble performance policy for ESX and block size tuning

    Alan Rutledge Newbie

      It my understanding from best practice doc(bpg_nimble_storage_vmware_vsphere5.pdf) that any LUN which will contain VMFS datastores should be set to use the ESX performance policy.


      It is also my understanding that this policy uses a 4k block size on nimble.


      My question is in regards to the block alignment document: https://connect.nimblestorage.com/docs/DOC-1185.  Does the table on page 3/4 also apply to VMDKs on VMFS volumes or does this only apply to volumes directly mounted using MS iSCSI initiator, etc?  If it does apply to VMFS should there be a column referencing VMware block size of 1MB(or 8k sub allocation) blocks, etc and that taken into account when discussing?





        • Re: Question on nimble performance policy for ESX and block size tuning
          Nick Dyer Navigator

          Hi Alan,


          Block alignment only really needs to be a concern if you're using VMFS volumes which were created using VMFS-3, or if you're using Windows 2003 (or a volume which was created on Windows 2003 and upgraded to Windows 2008). If it's VMFS-5 or a new volume created on Windows 2008 or later, then it *should* be properly aligned.


          If you're using VMware vSphere 5, please use "VMware ESX 5" as the performance policy rather than the "VMware ESX" version; this means that the latest changes to the limitations of VMFS-5 are able to be used (ie VMFS > 2TB in size).


          Support have a great tool called Coral (which is due to be integrated into the next rollout of Infosight) which allows for diving into alignment and latency of a volume to spot the problem. If you give Support a call or email they can give you this information if you have concerns.

          • Re: Question on nimble performance policy for ESX and block size tuning
            Alex Goltz Adventurer

            Hi Alan,

            I think you're on the right track with that table on 3/4 with that PDF.  For whatever its worth, I referenced that document when I was building our SQL servers with direct iSCSI to the Nimble volume.

            Personally, I think the document should be Block Alignment AND Sizes for Best Performance on Nimble Storage.  That might alleviate some confusion.

            This document is alot more helpful when configuring iSCSI direct connections and NTFS cluster sizes, than block alignment.  Hopefully that table makes it into the documentation, because I think alot of people might be setting it up incorrectly until they come across this PDF.


            You won't need this table if you are doing VMDK/VMFS datastores or RDMs.  (Those are 4KB I/O's with 1MB blocks on the storage, like you stated.  I think.)


            Does this help ?