Fixing storage misalignment – Part 3

Offline disk alignment using NetApp toll called mbralignment tool

In most cases offline alignment would be performed on old Linux or Solaris versions.

  • make sure VM is powered of and has no snapshots
  • SSH to ESX(i) box
  • change patch to datastore where misaligned virtual machine is located
  • alignment tools are located on /opt/ontap/santools/
  • do scan of the virtual machine VMDK FLAT file to make sure is misaligned, as you can see, first disk is not aligned. Offset is 32256 /4096 = 7.875 – as you may already know, offset should be dividable by 4096
[[email protected] suse01]# /opt/ontap/santools/mbrscan suse01_1-flat.vmdk
suse01_1-flat.vmdk p1 (LLVM)   lba:2048        offset:1048576  aligned:Yes
[[email protected] suse01]# /opt/ontap/santools/mbrscan suse01-flat.vmdk
suse01-flat.vmdk p1 (Linux)    lba:63  offset:32256    aligned:No
suse01-flat.vmdk p2 (LLVM)     lba:10474380    offset:5362882560       aligned:No
[[email protected] suse01]#
  • Time to align virtual machine disk, it will be SUSE 11.
[[email protected] suse01]# /opt/ontap/santools/mbralign suse01-flat.vmdk
Part    Type          old LBA    New Start LBA      New End LBA     Length in KB
P1      83               63               64         10474381          5237158
P2      8e         10474380         10474392        178257252         83891430

This tool does not check for the existence of Virtual Machine snapshots or linked clones.
The use of this tool on a vmdk file that has a snapshot or linked clone associated with it
can result in unrecoverable data loss and/or data corruption.
Are you sure that no snapshots/linked clones exist for this vmdk? (y/n)y
Creating a backup of suse01.vmdk
Creating a backup of ./suse01-flat.vmdk
Creating a copy the Master Boot Record
Working on partition P1 (2): Starting to migrate blocks from 32256 to 32768.
12801 read ops in 5 sec.  5.86% read (17.95 mB/s).  5.86% written (17.95 mB/s)
Working on P2 (3): Starting to migrate blocks from 5362882560 to 5362888704.
12801 read ops in 4 sec.  99.96% read (20.01 mB/s).  99.96% written (20.01 mB/s)
Working on space not in any partition: Starting to migrate blocks.
100.00 percent complete.  100.00 percent written. .
Making adjustments to ./suse01-flat.vmdk.
Adjusting the descriptor file.
[[email protected] suse01]#

It might take a longer while, depending how fast is the storage and how big is the machine. Start VM – but it will not boot 🙂 because mbr tool change block for root partition from 63 to 64.

grub prompt

grub prompt

Recover GRUB boot loader on Linux VM – in my case SUSE 11
  • Boot from ISO with SUSE 11 OS
  • From boot menu choose Rescue System
SUSE rescue system

SUSE rescue system

  • Login to rescue console as a root – without password
  • Type commands as below:
root (hd0,0)  #is comma not dot
setup (hd0)
GRUB fix

GRUB fix

  • Reboot VM
  • DONE

VM should boot correctly like on the figure below. Perform scan and aligned VM shouldn’t reported any more.

Boot menu from SUSE 11

Boot menu from SUSE 11


In case of problem with recovering VM after alignment, you can reconfigure VM to use virtual machine backup files

[[email protected] suse01]# ll
total 222977536
-rw------- 1 root root      6554112 Jul  4 00:30 suse01_1-ctk.vmdk
-rw------- 1 root root 107374182400 Jul  3 11:11 suse01_1-flat.vmdk
-rw------- 1 root root          582 Jul  4 00:30 suse01_1.vmdk
-rw------- 1 root root           13 Jun 28 14:00 suse01-aux.xml
-rw------- 1 root root      5571072 Jul  4 00:30 suse01-ctk.vmdk
-rw-r--r-- 1 root root  91268061184 Jul  4 15:40 suse01-flat.vmdk
-rw------- 1 root root  91268055040 Jul  3 16:19 suse01-flat.vmdk-mbralign-backup
-rw------- 1 root root         8684 Jul  3 16:19 suse01.nvram
-rw------- 1 root root          704 Jul  4 15:40 suse01.vmdk
-rw-r--r-- 1 root root          704 Jul  4 13:38 suse01.vmdk-mbralign-backup
-rw-r--r-- 1 root root           44 Jul  4 00:30 suse01.vmsd
-rwxr-xr-x 1 root root         4464 Jul  4 00:30 suse01.vmx
-rw-r--r-- 1 root root          262 Jun 28 16:25 suse01.vmxf
-rw-r--r-- 1 root root       677857 Jun 28 15:11 vmware-0.log
-rw------- 1 root root       241141 Jun 28 14:00 vmware-10.log
-rw------- 1 root root       277633 Jun 28 14:00 vmware-11.log
-rw------- 1 root root       171203 Jun 28 14:00 vmware-12.log
-rw------- 1 root root       247059 Jun 28 14:00 vmware-13.log
-rw------- 1 root root       770982 Jun 28 14:00 vmware-14.log
-rw------- 1 root root       658082 Jun 28 14:00 vmware-15.log
-rw-r--r-- 1 root root      1016018 Jul  3 16:19 vmware.log
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Artur Krzywdzinski

Artur is Consulting Architect at Nutanix. He has been using, designing and deploying VMware based solutions since 2005 and Microsoft since 2012. He specialize in designing and implementing private and hybrid cloud solution based on VMware and Microsoft software stacks, datacenter migrations and transformation, disaster avoidance. Artur holds VMware Certified Design Expert certification (VCDX #077).

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