Re: evms_clean...where's the metadata please?

[email protected] wrote on 03/26/2007 10:48:35 PM:

> Hi there,
>
> Having some issues here that appear to be related to left-over
> metadata that is not getting cleaned out when deleting RAID groups.
> It occurs most frequently when using "nested" RAID groups using
> md...for example, creating a RAID 10 using RAID 0 across multiple
> RAID 1's. After deleting the RAID groups and regions, I run
> evms_clean to wipe them further,

When you delete the RAID groups and regions the metadata would be wiped
out.  When you run evms_clean it should not find any RAID metadata to wipe
out.

> but if I create new RAID groups
> with these same hard drives, EVMS 2.5.5 almost always reports a
> degraded state from the get-go and some other incorrect information.
>
> I know evms_clean is undocumented, but is there source code
> available?

steved@steved:~/evms/engine2> find . -name evms_clean\*
./tests/evms_clean.c

> Better yet, can you tell me where (what sector range
> perhaps) on a hard drive the metadata is being stored? I'd be happy
> to write a script that nukes those sectors but I need some guidance
> here. Thanks!

The RAID metadata are stored near the end of the object.  I believe its
location is something like "take the size of the object, round down to the
next 64 KB boundary, then back up another 64 KB and put the metadata
there."  See plugins/md/md_super.h for the real calculations.

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