[linux-lvm] Question on RAID integrity limitations

Cyclic Group Z_1 cyclicgroup-z1 at yahoo.com
Wed Jun 7 05:41:56 UTC 2023

 Thank you for your reply! 
Ah ok, that makes sense. I think it is just a terminological confusion. In other contexts, restoring a lost hard drive in a degraded RAID array is called "rebuilding," but it seems here, it refers to reconstructing physical volumes that may contain corrupt data (`lvchange --rebuild`). If the replacement of a drive (in other contexts, rebuilding a degraded RAID array) is still possible through `lvconvert --replace` or `lvconvert --repair`, then my concerns are not an issue. I was worried that, by needing to turn off integrity during a rebuild, the future state of the array may be corrupt due to integrity not being active during the propagation of data to the new drive.
Regarding snapshots, that's wonderful news!

    On Monday, June 5, 2023 at 10:36:12 AM CDT, David Teigland <teigland at redhat.com> wrote:  
 On Sat, Jun 03, 2023 at 12:30:01AM +0000, Cyclic Group Z_1 wrote:
> The lvmraid documentation says the following: "To work around some
> limitations, it is possible to remove integrity from the LV, make the
> change, then add integrity again. (Integrity metadata would need to
> initialized when added again.) ... The following are not yet permitted
> on RAID LVs with integrity: lvreduce, pvmove, snapshots, splitmirror,
> raid syncaction commands, raid rebuild." Does this mean that RAID
> rebuilds can only be done with integrity temporarily turned off?

It refers specifically to running the command "lvchange --rebuild".  I'm
not entirely sure how important that command is, but I'd be happy to hear
more about its usefulness.

> This seems risky given that rebuilds are often when RAID arrays undergo the
> most stress and are thus vulnerable to failures/errors (namely, for
> parity RAID). Additionally, is the suggested workaround for snapshots to
> temporarily turn off integrity when taking/using snapshots?  Thank you!

Snapshots were recently enabled:


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