+ Post New Thread
Results 1 to 4 of 4
Hardware Thread, Disk Alignment in Technical; I'm just wondering if anyone else out there aligns their disk partitions? This is most applicable to virtual machines and ...
  1. #1
    DMcCoy's Avatar
    Join Date
    Oct 2005
    Location
    Isle of Wight
    Posts
    3,453
    Thank Post
    10
    Thanked 493 Times in 433 Posts
    Rep Power
    111

    Disk Alignment - Especially important for VMs!

    I'm just wondering if anyone else out there aligns their disk partitions? This is most applicable to virtual machines and Exchange stores but applies to SANs and normal RAID arrays, along with various other OS.

    It's to do with starting partitions on the 63rd sector, and how it doesn't align with the disk stripes. This means reads are often unnecessarily done across stripe boundaries.

    In Vista, it is done for you, I assume this will apply to 2008 server too. XP and 2003 do not, I don't think linux does either.

    There is a minimal, but real, performance hit of a few percent when the partition is not aligned. I came across this with my migration to ESX 3 as I hadn't aligned my partitions when my SAN was first set up (not to be confused with the SANs own alignment options!)

    If you create your VMFS partions on the LUN (or RAID) volume with Virtual Center 2.0 (or 2.5) then it will align to a 32k boundary for you, the console and scripted install do not (nor will the installer).

    Not only do the VMFS partitions have to be aligned, the virtual machine virtual disks need to be aligned too! This involves creating the disk on an existing server 2003 machine and using diskpar (not diskpart) to create an alligned partition, this disk is then assigned to the correct VM for use.

    It was quite a lot of work as its a destructive process and I had to move the data between my LUNs to eventually repartition them all!

    I'm not telling people "go and do this!" I'm simply curious with the larger number of ESX users we have now. (http://www.vmware.com/pdf/esx3_partition_align.pdf for the curious).

    David
    Last edited by DMcCoy; 1st February 2008 at 03:19 PM. Reason: Fine, I'll make a more interesting title!

  2. #2

    Geoff's Avatar
    Join Date
    Jun 2005
    Location
    Fylde, Lancs, UK.
    Posts
    11,803
    Thank Post
    110
    Thanked 583 Times in 504 Posts
    Blog Entries
    1
    Rep Power
    224
    I use GNU parted for partition creation. It automatically aligns the file system partitions to the correct boundaries..

  3. #3

    Join Date
    Jan 2006
    Location
    Surburbia
    Posts
    2,178
    Thank Post
    74
    Thanked 307 Times in 243 Posts
    Rep Power
    115
    I've done that on Exchange boxes, but have also encountered a somewhat plausible claim that alignment may do very little for disks nowadays because of all the magic they do behind the scenes to get those lovely big modern capacities i.e. the text-book disk geometry model is virtual, not what really happens on the disk.

    I'll let someone else figure out which story is correct.

  4. #4
    DMcCoy's Avatar
    Join Date
    Oct 2005
    Location
    Isle of Wight
    Posts
    3,453
    Thank Post
    10
    Thanked 493 Times in 433 Posts
    Rep Power
    111
    Quote Originally Posted by Geoff View Post
    I use GNU parted for partition creation. It automatically aligns the file system partitions to the correct boundaries..
    Ubuntu server doesn't align correctly when installing

    Quote Originally Posted by PiqueABoo View Post
    I've done that on Exchange boxes, but have also encountered a somewhat plausible claim that alignment may do very little for disks nowadays because of all the magic they do behind the scenes to get those lovely big modern capacities i.e. the text-book disk geometry model is virtual, not what really happens on the disk.

    I'll let someone else figure out which story is correct.
    It's about making additional stripe crossings with raid (http://support.microsoft.com/kb/929491 has some info)

    My testing shows a increase of peak throughput of around 6% with my SAN.

SHARE:
+ Post New Thread

Similar Threads

  1. JCE Editor default alignment
    By patshaw101 in forum EduGeek Joomla 1.0 Package
    Replies: 6
    Last Post: 26th February 2008, 03:43 PM
  2. Smartboard Alignment
    By gshaw in forum Hardware
    Replies: 20
    Last Post: 16th January 2008, 12:44 PM
  3. Whiteboard alignment
    By witch in forum Hardware
    Replies: 18
    Last Post: 17th October 2007, 06:25 PM
  4. RM Disk to Disk to Tape Backup Solution
    By Chris in forum General Chat
    Replies: 0
    Last Post: 2nd July 2007, 10:14 AM
  5. Disk to Disk to Tape backup. How do you do it?
    By trekmad in forum How do you do....it?
    Replies: 0
    Last Post: 30th May 2007, 07:49 PM

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •