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Re: [linux-lvm] Possible to raise Max LV?

Dave Alden writes:
>   I'm hoping to use LVM with my hardware RAID array so I can take snapshots
> of the filesystem for backups.  What I'm worried about is that my current
> array is 240GB, so the next drive I add will take it over 256GB which (if
> I'm reading the HOWTO correctly) means that I won't be able to use LVM
> anymore (since it's being presented as one drive).  Is there someway to
> get around the 256GB limit (or did I misunderstand this completely? :-)

The max LV size is dependent upon the PE size that you select at VG
creation time.  This is because there is a limit of 64k PEs per LV.

64k = 2^16, 4MB = 2^22 -> 2^16 * 2^22 = 2^38 = 2^8 * 2^30 = 256GB

There is no way to fix this, unfortunately, without backup/restore or
having enough disk space to make a new VG with larger PE size and
then copy your filesystem over.  You can only have 1 PE size in a VG,
so it is not possible to do a "pvmigrate" to a larger PE size.

If you don't have a single LV > 256GB then you do not have a problem.
The 256GB limit is per LV.

Cheers, Andreas
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert

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