Hi,
thank you very much for your quick response! Ok, so putting the DB/WAL
on the NVMe drives could be beneficial. What happens if your SSD with
the DB/WAL on it breaks? I assume you configured some type of
(double/triple, etc.) replication?
Regards,
Mevludin
Am 22.10.2021 um 11:47 schrieb Zakhar Kirpichenko:
Hi,
It is my experience with Bluestore that even if you put DB/WAL on a
very fast SSD (NVME in my case), the OSD will still refuse to write
faster than the storage device (HDD) can write on average. This is a
bummer because the behavior is very different from Filestore, which
could buffer write bursts on SSD, defer and write them to HDD later
on. Having DB/WAL on SSD still helps with general latency, though.
With regards to SSD cache, putting an SSD cache tier with Ceph is
possible, but be prepared that it doesn't quite work the way you would
expect it to, that its performance is very highly dependent on your
workload, and that it may cause sudden issues: for example, with
16.2.x my VMs would randomly lose access to their RBD images during
intense writes through a cache tier. Putting a cache tier for an OSD
device with bcache, dm-cache, etc may be a better and more stable
option, although it is unlikely that you will be able to automate this
with Ceph toolset.
Best regards,
Z
On Fri, Oct 22, 2021 at 12:30 PM Mevludin Blazevic
<mblaze...@uni-koblenz.de <mailto:mblaze...@uni-koblenz.de>> wrote:
Dear Ceph users,
I have a small Ceph cluster where each host consist of a small
amount of
SSDs and a larger number of HDDs. Is there a way to use the SSDs as
performance optimization such as putting OSD Journals to the SSDs
and/or
using SSDs for caching?
Best regards,
Mevludin
--
Mevludin Blazevic, M.Sc.
University of Koblenz-Landau
Computing Centre (GHRKO)
Universitaetsstrasse 1
D-56070 Koblenz, Germany
Room A023
Tel: +49 261/287-1326
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--
Mevludin Blazevic, M.Sc.
University of Koblenz-Landau
Computing Centre (GHRKO)
Universitaetsstrasse 1
D-56070 Koblenz, Germany
Room A023
Tel: +49 261/287-1326
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