27 Feb
2020
27 Feb
'20
7:08 p.m.
Hi everyone,
we currently have 6 OSDs with 8TB HDDs split across 3 hosts.
The main usage is KVM-Images.
To improve speed we planned on putting the block.db and WAL onto NVMe-SSDs.
The plan was to put 2x1TB in each host.
One option I thought of was to RAID 1 them for better redundancy, I don't know how
high the risk is of corrupting the block.db by one failed SSD block.
Or should I just one for WAL+block.db and use the other one as fast storage?
Thank you all very much!
Christian
27 Feb
27 Feb
10:28 p.m.
Christian;
What is your failure domain? If your failure domain is set to OSD / drive, and 2 OSDs
share a DB / WAL device, and that DB / WAL device dies, then portions of the data could
drop to read-only (or be lost...).
Ceph is really set up to own the storage hardware directly. It doesn't (usually) make
sense to put any kind of RAID / JBOD between Ceph and the hardware.
Thank you,
Dominic L. Hilsbos, MBA
Director - Information Technology
Perform Air International Inc.
DHilsbos(a)PerformAir.com
www.PerformAir.com
-----Original Message-----
From: Christian Wahl [mailto:wahl@teco.edu]
Sent: Thursday, February 27, 2020 12:09 PM
To: ceph-users(a)ceph.io
Subject: [ceph-users] SSD considerations for block.db and WAL
Hi everyone,
we currently have 6 OSDs with 8TB HDDs split across 3 hosts.
The main usage is KVM-Images.
To improve speed we planned on putting the block.db and WAL onto NVMe-SSDs.
The plan was to put 2x1TB in each host.
One option I thought of was to RAID 1 them for better redundancy, I don't know how
high the risk is of corrupting the block.db by one failed SSD block.
Or should I just one for WAL+block.db and use the other one as fast storage?
Thank you all very much!
Christian
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28 Feb
28 Feb
8:58 a.m.
Hi Christian,
El 27/2/20 a las 20:08, Christian Wahl escribió:
Hi everyone,
we currently have 6 OSDs with 8TB HDDs split across 3 hosts.
The main usage is KVM-Images.
To improve speed we planned on putting the block.db and WAL onto NVMe-SSDs.
The plan was to put 2x1TB in each host.
One option I thought of was to RAID 1 them for better redundancy, I don't know how
high the risk is of corrupting the block.db by one failed SSD block.
It's hard
to tell without more information, but what is for you "improve
speed"? Is that latency or throughtput?
I don't think those NVMe disk used as block.db and WAL will help much in
terms of throughtput. They may help a bit with latency though.
For more throughtput you need more disks. Those 8TB disks are too big
and too few.
Wouldn't it be better to use all NVMe disks as OSDs and create two
tiers? One pool based on NVMe will be fast and the pool based on HDDs
will be like now...
Or should I just one for WAL+block.db and use the
other one as fast storage?
Depends on your use case, but I don't think it makes sense to create a
RAID1 with NVMe disks.
Have you checked current DB and WAL use on those OSDs?
Cheers
Eneko
--
Zuzendari Teknikoa / Director Técnico
Binovo IT Human Project, S.L.
Telf. 943569206
Astigarragako bidea 2, 2º izq. oficina 11; 20180 Oiartzun (Gipuzkoa)
www.binovo.es
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2 comments
3 participants
participants (3)
-
Christian Wahl -
DHilsbos＠performair.com -
Eneko Lacunza