EMC:setting bad block relocation

[gene egournov_1]

Hello,

a few days ago I created new volume group using 4 disks attached to EMC array, and then logical volumes on it.
Now I'd like to change bad block relocation policy as follows:

lvchange -r N /dev/vgXX/lvolXX

Is it safe to do this now?
How do I check to see if bad block directory has been already created?

thanks in advance.

[James R. Ferguson · Accepted solution]

Hi:

Yes, you can issue the 'lvchange' to turn off bad block reallocation at any time. An 'lvdisplay' will show you the current state.

Document #A5724882 notes that LVM reserves special alternate storage space at the end of the disk for handling bad block errors. The alternate storage space prevents a fatal error if a write fails, by providing an alternate block to complete the operation. If, however, your disk controller already supports bad block relocation (also called 'hardware sparing'), you may consider not using LVM's bad block relocation mechanism. A good explanation of bad blocks is in document #UNX1000316.

...JRF...

[Rita C Workman]

Yes, I believe you can. And in fact (based on what our EMC Engineer said) you should turn off the LVM bad block re-allocation on all EMC logical volumes. You can do this when you create the logical volumes or with a lvchange; basically the same procedures as when you make any change to an lvol.
Per the information passed on by EMC:
EMC disk arrays have a bad block re-allocation built into their system...when you leave active the bad block reallocation policy in LVM this can create a conflict. The system may (more than likely will not) not know where to find the data.

regards,

[gene egournov_1]

Thank you both for your detailed replies.

gene egournov