[linux-lvm] Solving the "metadata too large for circular buffer" condition
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Wed Nov 24 23:07:57 UTC 2010
Taking another look, my estimate of required metadatasize
might be off by a factor of five or so. 128K might be sufficient
for 100 LVs, depending on fragmentation and such.
Still, the history of computer science is largely a story
of problems caused by people thinking they'd allocated plenty
of space. Today you can't fdisk a drive or array larger than
2TB because someone thought 32 bits would plenty. Probably
best to allocate 100 times as much as you think you'll ever
need - a few MB of disk space is cheap.
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On 11/24/2010 02:28:11 PM, Andrew Gideon wrote:
> We've just hit this error, and it is blocking any expansion of
> or creation of new volumes.
> We found:
> which appears to describe a solution. I'm doing some reading, and
> set up a test environment to try things out (before doing anything
> to production). But I'm hoping a post here can save some time (and
> First: The referenced thread is two years old. I don't suppose
> there's a
> better way to solve this problem today?
> Assuming not...
> I'm not sure how metadata is stored. It seems like, by default, it is
> duplicated on each PV. I'm guessing this because one can't just add
> PVs (with larger metadatasize values), but one must also remove the
> metadata. Is that right?
> Are there are consequences to removing the metadata from most of the
> physical volumes? I've six, so I'd be adding a seventh and eighth
> for redundancy, though the PVs are all built on RAID sets).
> The "pvcreate --restorefile ... --uuid ... --metadatacopies 0" command
> would be executed on the existing 6 physical volumes? No data would
> lost? I want to be *very* sure of this (so I'm not trashing an
> What is the default metadatasize? Judging from lvm.conf, it may be
> 255 Megabytes? Is there some way to guestimate how much space I
> expect to be using? I thought perhaps pvdata would help, but this is
> apparently LVMv1 only.
> [Unfortunately, 'lvm dumpconfig' isn't listing any data in the
> There's also mention in the cited thread of reducing fragmentation
> pvmove. How would that work? From what I can see, pvmove will move
> segments. But even if two segments are moved from dislocated
> to immediately adjacent locations, I see nothing which says that these
> two segments would be combined into a single segment. So I'm not
> how fragmentation can be reduced.
> Finally, there was mention of changing lvm.conf - presumably,
> metadata.dirs - to help make more space. Once lvm.conf is changed,
> is that change made live? Is a complete reboot required, or is there
> quicker way?
> Thanks for any and all help...
> linux-lvm mailing list
> linux-lvm at redhat.com
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
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