LVM bad block relocation (BBR)

[Jojo Castro]

Hi all, I have hp server rx7640 with HP-UX 11.23 as OS attached to EMC storage. EMC guys are recommending that LVM bad block relocation (BBR) should be disabled, and the LVM mechanism for marking blocks defective when a medium error is returned should also be disabled for all LVM volumes on EMC devices.

Questions:
1.) How can i know if LVM is currently enabled (which I know its enabled because i configured the disks by default)
2.) How can i disable it when disks are already in use and mounted? Can i do it online?

Thanks!

[Jeff_Traigle · Accepted solution]

We recently implemented EMC storage. To disable logical volume bad block relocation, use the following command:

lvchange -r N /dev/vg01/lvol1

(Replace /dev/vg01/lvol1 with your LV path, of course.)

This change can be made online. To see the state of the policy, see the "Bad block" entry in the lvdisplay output for the LV.

[Jojo Castro]

Thanks Jeff

[Turgay Cavdar]

This is a fake message, BBR is obsolete for hp-ux 11.23.

"This is an obsolete flag available only to provide compatibility with prior HP-UX releases.LVM bad block relocation feature,however for compatibility reasons the value is maintained as a logical volume attribute.Displaying the logical volume attributes will show the value of the flag selected.However, regardless of the selection, no new relocations will be done."

[Jojo Castro]

Hi Turgay,

Our EMC guys are fully aware that we are running in HP-UX 11.23
So why you think they still insist to change it?
Any other opinion whith this?
"Fake message?" :)

[Turgay Cavdar]

Hi Jolo,
You are possibly running emcgrab on the server, and i think EMC guys don't populate these scripts for this kind of changes. But you should ask this question to EMC, why they dont populate this scripts? :)

[Doug O'Leary]

Damn, someone beat me to the punch. This is a meaningless change in HPUX 11.23.

I occasionally have this conversation with our lead SAP/Basis guy who usually wants this turned off on all LVs regardless of import just so the LVs look the same.

I would imagine this'll depend on your personality. If you like the EMC guys and aren't very combative, turn it off just to avoid the argument. If you like to watch vendors squirm, show them the section of the man page and tell them you want an updated emcgrab.

Doug O'Leary

[Torsten.]

>> EMC guys are recommending that LVM bad block relocation (BBR) should be disabled


HP guys say the same, since disks and arrays can do this much better than LVM could ever do.



# lvdisplay -v /dev/vg00/lvol1|more
--- Logical volumes ---
LV Name /dev/vg00/lvol1
VG Name /dev/vg00
LV Permission read/write
LV Status available/syncd
Mirror copies 1
Consistency Recovery MWC
Schedule parallel
LV Size (Mbytes) 400
Current LE 25
Allocated PE 50
Stripes 0
Stripe Size (Kbytes) 0
Bad block off <<=====

[Jojo Castro]

Hi guys,

Sorry for the late reply.
So bottom line, BBR lvm parameter is already obsolete in HP-UX 11.23? and changing it from on to off or vise versa is already a no bearing?

[Turgay Cavdar]

You can do it online but as i said before it does not provide the BBR feature.