Hi all,
El 4/2/21 a las 11:56, Frank Schilder escribió:
- three servers
- three monitors
- 6 osd (two per server)
- size=3 and min_size=2
This is a set-up that I would not run at all. The first one is, that ceph lives
on the law of large numbers and 6 is a small number. Hence, your OSD fill-up
due to uneven distribution.
What comes to my mind is a hyper-converged server with 6+ disks in a RAID10
array, possibly with a good controller with battery-powered or other
non-volatile cache. Ceph will never beat that performance. Put in some extra
disks as hot-spare and you have close to self-healing storage.
Such a small ceph cluster will inherit all the baddies of ceph (performance,
maintenance) without giving any of the goodies (scale-out, self-healing, proper
distributed raid protection). Ceph needs size to become well-performing and pay
off the maintenance and architectural effort.
It's funny that we have multiple clusters similar to this, and we and
our customers couldn't be happier. Just use a HCI solution (like for
example Proxmox VE, but there are others) to manage everything.
Maybe the weakest thing in that configuration is having 2 OSDs per node;
osd nearfull must be tuned accordingly so that no OSD goes beyond about
0.45, so that in case of failure of one disk, the other OSD in the node
has enough space for healing replication.
When deciding min_size, one has to balance availability (failure during
maintenance of one node with min_size=2) vs risk of data loss (min_size=1).
Not everyone needs to max SSD disk IOPS; having a decent, HA setup can
be of much value...
Cheers
--
Eneko Lacunza
Zuzendari teknikoa | Director técnico
Binovo IT Human Project
Tel. +34 943 569 206 | https://www.binovo.es
Astigarragako Bidea, 2 - 2º izda. Oficina 10-11, 20180 Oiartzun
https://www.youtube.com/user/CANALBINOVO/
https://www.linkedin.com/company/37269706/
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