LVM and VxVM

SAN & Bad Block Relocation Policy

 
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Justin Willoughby
Regular Advisor

SAN & Bad Block Relocation Policy


I have read that I should disable bad block relocation policy for disks on my HP-UX box that are on/connected via a SAN that is connected via Fibre Channel because the SAN array does the bad block relocation for me. If so and believe it is, should I do a `lvchange -r n /dev/vgname/lvname` or `lvchange -r N /dev/vgname/lvname` ?

Thanks!

- Justin
5 REPLIES 5
Sridhar Bhaskarla
Honored Contributor
Solution

Re: SAN & Bad Block Relocation Policy

Hi Justin,

It does not really matter as long as the LVM does not attempt to relocate a bad block which is accomplished by both options.

-r N does not even maintain a bad block directory which is a preferred option to me as we dont' want to care about the bad blocks at all.

-Sri
You may be disappointed if you fail, but you are doomed if you don't try
James R. Ferguson
Acclaimed Contributor

Re: SAN & Bad Block Relocation Policy

Hi Justin:

For an EMC2 SAN, you want to use '-N' which prevents bad block relocation *and* the Bad Block Directory.

When done, an 'lvdisplay' of the changed logical volume will show "Bad block NONE".

Regards!

...JRF...
Marco Santerre
Honored Contributor

Re: SAN & Bad Block Relocation Policy

If you don't want Unix to handle your bad block reallocation at all, you should definitely use :

#lvchange -r N /dev/vgname/lvname
Cooperation is doing with a smile what you have to do anyhow.
Rita C Workman
Honored Contributor

Re: SAN & Bad Block Relocation Policy

Depends on the array...we have EMC and for them we turn off the BadBlock Reallocation (since EMC handles it). To leave it on, would create confusion between the server and the array.

The command I have always used is the lvchange -r N ....

Rgrds,
Rita
Justin Willoughby
Regular Advisor

Re: SAN & Bad Block Relocation Policy

Great!

Thanks All, that answers my question!

- Justin