Mailinglist Archive: opensuse (1470 mails)

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Re: [opensuse] any real-life experiences with bache / dm-cache and ssd ?
On Don, 2016-02-11 at 10:55 +0100, Per Jessen wrote:
jdd wrote:

Le 11/02/2016 08:23, Per Jessen a écrit :
I was studying bcache yesterday and just wondered if anyone had
any
real-life experiences to share?


yes, and not that good

http://dodin.info/wiki/pmwiki.php?n=Doc.UsingBcache

too complicated to the fuss

Hmm, I was hoping for some details about improved IO rates and such.
I
have some aging storage servers and I was wondering if I could
improve
the IO rates by adding a SSD cache instead of replacing the
controllers
or even the whole thing.

I have been using bcache for a couple of years, and I'm very happy with
it.

My setup is a 4TB md RAID1 volume with a 120GB bcache on top of it,
which in turn is used as an LVM physical volume. That is, about 3% of
the total PV capacity can be cached, and all LVs share the cache.

Because the cache is small, it only serves to speed up random-access
reads of the active working set, and to speed up most writes (writeback
cache mode).

The net effect is that, even though all data (including user home
directories) is stored on a pair of spinning disks, the cache manages
to hide that fact well enough to make the machine feel very snappy in
use - it's close enough to a real SSD for my needs.

Sorry, I can't give any concrete numbers to back up my experiences.

\Olav
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