[linux-lvm] Problem with partially activate logical volume
Ken Bass
daytooner at gmail.com
Fri Aug 5 12:42:40 UTC 2022
Zdenek: thanks. That makes more sense. I will try after (re-)cloning. Give it a day or so.
Ken
On Aug 5, 2022, 7:03 AM, at 7:03 AM, Zdenek Kabelac <zdenek.kabelac at gmail.com> wrote:
>Dne 03. 08. 22 v 23:31 Ken Bass napsal(a):
>>
>> That's pretty much it. Whenever any app attempts to read a block from
>the
>> missing drive, I get the "Buffer I/O error" message. So, even though
>my
>> recovery apps can scan the LV, marking blocks on the last drive as
>> missing/unknown/etc., they can't display any recovered data - which I
>know
>> does exist. Looking at raw data from the apps' scans, I can see
>directory
>> entries, as well as files. I'm sure the inodes and bitmaps are still
>there for
>> some of these, I just can't really reverse engineer and follow them
>through.
>> But isn't that what the apps are supposed to do?
>
>As mentioned by my previous email you shall *NOT* fix the partially
>activated
>device in-place - this will not lead to good result.
>
>User should copy the content to some valid storage device with the same
>size
>as he tries to recover.
>
>You can 'partially' activate device with "zero" filler instead of
>"error"
>(see the lvm.conf setting: missing_stripe_filler="...") - this way
>you
>will just 'read' zero for missing parts.
>
>Your another 2nd. option is to 'correct' the VG by filling missing PV
>with a
>new one with preferable zeroed content - so you will not read 'random'
>garbage
>in places this new PV will fill the space after your missing PV.
>Although even in this case - I'd still run 'fsck' on the snapshot
>created on
>top of such LV to give you another chance of recovery if you will pick
>a wrong
>answer (since fsck might be 'quite' interactive when doing such
>large-scale
>repair)
>
>
>> Sorry I haven't replied sooner, but it takes a long time (days) to
>clone, then
>> scan 16Tb...
>>
>> So, please any suggestions are greatly appreciated, as well as
>needed.
>>
>> ken
>>
>> (I know: No backup; got burned; it hurts; and I will now always have
>backups.
>> 'Nuf said.)
>
>Before you run your 'fsck' create a snapshot of your newly created
>'backup'
>and make all the repair actions in the snapshots.
>
>Once you are 'satisfied' with 'repaired' filesystem you can then
>'merge'
>snapshot back to your origin and use it.
>
>Regards
>
>Zdenek
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