Aligning VMFS and Linux using fdisk

The alignment procedure for VMFS and the Linux file system (whether it be ext3, ext2, riser, xfs etc.) is much the same as any other Linux file system.  We’ll use fdisk’s expert mode to create a new partition with an aligned starting block and then format the file system.  You should use this procedure for not only VMFS, but for your Linux virtual machines as well (changing the type in step 7 to 83.)

1. If you’re not already on the service console as the root user, begin by becoming root
   
   

   $ whoami thirt $ su - root Password:

   
   
2. Run fdisk on the device you would like to align.  Depending on your configuration, this device will be different.  Use the ‘fdisk –l’ to list all available devices; replacing ‘/dev/disks/vmhba32\:0\:0\:0’ in the command below with your device.
   
   

   $ fdisk /dev/disks/vmhba32\:0\:0\:0

   Note that a ‘:’ is a special character in the Linux shell and must be escaped with a ‘\’
   
   
3. Create a new partition
   
   

   Command (m for help): n

   
   
4. Choose ‘p’ for a new primary partition
   
   

   Command action e extended p primary partition (1-4) p

   
   
5. When asked for the partition number, enter ‘1’
   
   

   Partition number (1-4): 1

   
   
6. Use all the defaults by pressing enter at the prompts
   
   

   First cylinder (1-1088, default 1): Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-1088, default 1088): Using default value 1088

   
   
7. The VMFS file system uses the type fb.  Change the type to ‘fb’ on the new partition.  
   
   

   Command (m for help): t Selected partition 1 Hex code (type L to list codes): fb Changed system type of partition 1 to fb (Unknown)

   Note: If you were working with a traditional Linux partition, you would use type ‘83’ – the Linux file system.
   
   
8. Enter expert mode
   
   

   Command (m for help): x

   
   
9. Change the start block to a value that aligns with your stripe element size.  I like to use a start block of 2048 (2048 = 1024KB), ESX v3.x and later default to 128 (128 = 64KB) or as we have already said, you could use a value provided by your storage admin.
   
   

   Expert command (m for help): b Partition number (1-4): 1 New beginning of data (63-8385929, default 63): 2048

   
   
10. Commit the changes to disk
    
    

    Expert command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.

    
    
11. If you are formatting a VMFS for VMware, you should use vmkfstools to format your file system.  If you are formatting a Linux file system, you should use mke2fs or a similar tool to format your file system.  It goes without saying that formatting a file system will destroy any existing data on the device so make absolute certain your working with the correct disk!
    
    
    • To format a newly created VMFS,  use the following syntax replacing ‘/dev/disks/vmhba32\:0\:0\:0\:1’ in the command below with your device and partition number.
      
      

      # vmkfstools –C  vmfs3 –b 4m /dev/disks/vmhba32\:0\:0\:0\:1

      Note that ‘:’ is a special character in the Linux shell and must be escaped with a ‘\’
      
      
    • The formatting of a Linux file system can be slightly more complex due to the many different file systems and parameters offered like journaling.  We cannot cover all the different file systems and their options, but for most, ext3 is an excellent choice (includes journaling.)  The following syntax will format a file system as ext3, replace '/dev/sda1' with the device and partition you would like formatted.
      
      

      # mke2fs -j /dev/sda1

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Andre  - Nice step-by-step guide... |15/01/2010 14:12:22 I already read various articles about disk alignment. Your's is the one I bookmarked. Nice job. BTW, it seems someone changed a setting in step 8 and did not replace the picture in step 9. (2048 blocks should really not result in a 128 blocks offset;-))) Reply | Quote

Travis  - Nice write up |27/01/2010 11:02:46 Very nice write on disk alignment. I followed all the steps and when I went to install Windows I pressed enter in step 13 of your guide and the next screen asked me if I wanted to format the partition. Should this happen? Reply | Quote

Anonymous |03/02/2010 15:36:41 In step 11, command Code: # vmkfstools –C –createfs vmfs3 –b 4m /dev/disks/vmhba32\:0\:0\:0\:1 should looks like Code: # vmkfstools –C vmfs3 –b 4m /dev/disks/vmhba32\:0\:0\:0\:1 One should use "-C" or "--createfs". Reply | Quote

admin |03/02/2010 20:20:40 Nice catch! I've updated step #11 to reflect the change. Thanks! -Tom Reply | Quote

ericgc |18/02/2010 10:28:51 how come that command is not in step 11 anymore? Reply | Quote

Anonymous |26/02/2010 03:19:52 Hello, Does this apply to windows 2008 as well? /Nick Reply | Quote

thirt |03/03/2010 12:08:48 Hi Nick, No, Microsoft finally got around to fixing this in Windows 2008. I guess they received enough fan mail on the topic to address it. Best -Tom Reply | Quote

amikolajczyk  - IT Manager |08/10/2010 07:53:16 Hi, could you explain this a little more? What was the "this" that got fixed in 2008? Is it no longer necessary to do this in Windows 2008? I just followed your steps for a 2008 R2 VM and it failed to get past POST. I checked a recently deployed 2008 R2 server with your alignment check script and it reported everything was aligned A-OK even though I didn't manually do any manual steps at all. Thanks for this guide, I read a lot of them and this was hands-down the best explanation along with the best step-by-step guide. Regards, AJM Reply | Quote

Berni |28/08/2010 08:39:56 Great article about disk aligment. Thanks! But how can I extend an existing volume with the right aligment? When I extend the volume in VIC, the second disk is not aligned Reply | Quote

victor |02/01/2011 18:18:56 If I were to clone the aligned VM does the alignment follow or not? Reply | Quote

Denis |15/02/2011 14:00:06 Hi, Tom! Thanks. But i don't understand, why we align a windows partition of virtual machine, if vmdk-flat-files already aligned, because they are consist of 1MB clusters of VMFS file system. Reply | Quote

Anthony Vandewerdt |06/04/2011 23:11:02 Hi. Great pictures. You make the statement: NTFS is formatted in blocks ranging from 1MB to 8MB Do you mean VMFS? If I check here, NTFS uses clusters that are nowhere near that big: http://support.microsoft.com/kb/140365 Reply | Quote

erski  - Partition 1 has different physical/logical beginni |19/11/2011 01:46:22 I've made changes to disk step by step and I got this error: Disk /dev/sda: 4294 MB, 4294967296 bytes 255 heads, 63 sectors/track, 522 cylinders, total 8388608 sectors Units = sectors of 1 * 512 = 512 bytes Device Boot Start End Blocks Id System /dev/sda1 * 2048 224909 111431 83 Linux Partition 1 has different physical/logical beginnings (non-Linux?): phys=(0, 1, 1) logical=(0, 32, 33) /dev/sda2 224910 2329424 1052257+ 82 Linux swap / Solaris /dev/sda3 2329425 8385929 3028252+ 83 Linux Any idea how to resolve the problem? Reply | Quote

Mark W |12/02/2012 19:26:15 Hi, you mention in the article that once a windows partition is created and windows installed, you cannot change the offset. This is incorrect. You can boot off a gparted live cd, add a 2MB offset, then once its done that, change it to 1MB offset and then it aligns correctly. The two step process is necessary due to the way Gparted calculates the space. Reply | Quote

Magik  - Sr Systems Engineer |22/02/2012 11:57:45 If you can get your hands on a tool called MBRALIGN from NetApp Host Utilities for ESX then you can use this to run against VMDK files to fix the offset of existing virtual disks. It takes advantage of the fact that your partition is a VMDK and simply fixes the VMDK. Rick Reply | Quote

C. Beerse  - re: |25/04/2012 08:30:05 victor wrote: If I were to clone the aligned VM does the alignment follow or not? Depends on the clone tool: Most (older) tools just do a block copy of the guest disks. Hence, the allignment does not change. From vmware-converter 5.x (and workstation 8?) there is an option that optimizes the disk allignment. That updates the allignment to the conversion target. Current versions of other (vmware based) converters do the same. Reply | Quote

C. Beerse  - re: IT Manager |25/04/2012 08:33:36 amikolajczyk wrote: Hi, could you explain this a little more? What was the "this" that got fixed in 2008? Is it no longer necessary to do this in Windows 2008? I just followed your steps for a 2008 R2 VM and it failed to get past POST. As far as I know, msW2k8 and newer installations start with an 1 MByte offset for this allignment by default. That is with disks over a (relative small) size. If you create a realy small filesystem (less than 1 GB) it is reported the 63KByte first block missallignment is still there. I can imagine microsoft has done this because as a result of its own virtualisation business. I donnot have the impression this allignment is some active optimum. Reply | Quote

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