Discussion:
[linux-lvm] Quick question regarding lvm-cache
Devin Vance
2015-11-21 23:10:53 UTC
Permalink
Greetings,

Short version:

Is there anyway to adjust the cache blocksize of the lvm cache with the
lvm tools?

Long version:

I have been exploring the new lvm-cache features within rhel7 (tech
preview, I know), and with a cache of 1.4TiB in size I noticed these
warnings within the logs.

device-mapper: cache: You have created a cache device with a lot of
individual cache blocks (1638400) All these mappings can consume a lot
of kernel memory, and take some time to read/write.Please consider
increasing the cache block size to reduce the overall cache block count.

However, I cannot find any straightforward method with which to adjust
this cache block size. I did find this documentation which explains how
to do so with device mapper:
https://www.kernel.org/doc/Documentation/device-mapper/cache.txt Is
there anyway to do this with the lvm tools, or is this yet to be developed?


Many thanks,
Devin
Mike Snitzer
2015-11-23 15:55:15 UTC
Permalink
On Sat, Nov 21 2015 at 6:10pm -0500,
Post by Devin Vance
Greetings,
Is there anyway to adjust the cache blocksize of the lvm cache with
the lvm tools?
Kind of amazing that the lvmcache man page doesn't touch on
this... there is an opportunity there ;)

Anyway, lvcreate's -c argument (aka chunksize) is re-used to specify a
different cache blocksize.

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