mbralign on Steroids

Much of the customer engagements I work on involve migrating VMware guests from other vendors storage onto NetApp.  Because most other vendors are ignorant or deceptively quiet about importance of proper alignment on VMware, one of the most important things we do during a migration is fix VMware guest alignment.

You can get more information about guest alignment and mbralign HERE and HERE. That is not the purpose of this blog.

Unfortunately, since MBRAlign by default uses the ESX console, a workaround is necessary to align guest in an ESXi environment. The workaround involves using a linux guest to mount the NFS datastore and perform mbrscan and mbralign tasks from the guest. What is lesser-known is that the same workaround can seriously boost the performance of mbralign jobs even in non-ESXi environments. 

Vmware limits the resources available to ESX consoles to improve guest performance.  This means mbralign jobs will also be limited in performance when run on the ESX console.  If you have dozens or hundreds of VMs to align and are under shorter maintenance windows or just don’t want to be up all night doing alignments, try running mbralign from a Linux guest.

I had a customer this week who saw mbralign performance improve from 10MB/s to 80MB/s.  Definitely worth it for the hundreds of VMs to be aligned as they move them to NetApp.

Sorry, this approach doesn’t work for VMFS datastores, in that case, try increasing the mbralign block size (--bs) or consider increasing the resource limits for the ESX console.

Happy Aligning!

Comments

[Leif]

Mike,
Great idea and thanks for mentioning this. I admit I'm more of a Windows guy than a Linux guy. Do you have suggested mount options for mounting NetApp exports onto Linux? For my basic filer administrative work, I use these options to my Linux box:
mount -o rw,bg,vers=3,tcp,timeo=600,rsize=32768,wsize=32768,hard,intr

I took those options from pg. 22 of this TR:
http://www.netapp.com/us/library/technical-reports/tr-3183.html
I noticed the default mount in the Ubuntu release I'm using is soft which I didn't want to do.

[Mike Richardson]

Thanks Leif,

Those mount options should work OK. I would definitely recommend mounting "hard" as a general best practice, as you mentioned.

Good luck and feel free to reply with your results!

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Hi, we are aligning all our VMs with Netapp's mbralign tool.

We fix the linux grub with a Rescue "super grub" CD - but this does not work on the Solaris VMs

Error is: "Error 6 Mismatched or corrupt version of stage1/stage2"

I tried the manual steps (specifying the a "slice" someone mentioned in a solaris forum):

grub> root (hd0,0,a)
grub> setup (hd0)

but got the same error
Has anyone successfully aligned a Solaris VM??

thanks