We kind of turned the crushmap inside out a little bit.
Instead of the traditional "for 1 PG, select OSDs from 3 separate data
centers" we did "force selection from only one datacenter (out of 3) and
leave enough options only to make sure precisely 1 SSD and 2 HDD are
selected".
We then organized these "virtual datacenters" in the hierachy so that
one of them in fact contain 3 options that lead to 3 physically separate
servers in different locations.
Every physical datacenter has both SSD's and HDD's. The idea is that if
one datacenter is lost, 2/3 of the SSD's still remain (and can be mapped
to by marking the missing ones "out") so performance is maintained.
Den 2018-01-29 kl. 13:35, skrev Niklas:
Yes.
It is a hybrid solution where a placement group is always located on
one NVMe drive and two HDD drives. Advantage is great read performance
and cost savings. Disadvantages is low write performance. Still the
write performance is good thanks to rockdb on Intel Optane disks in
HDD servers.
Real world looks more like I described in a previous question
(2018-01-23) here on ceph-users list, "Ruleset for optimized Ceph
hybrid storage". Nobody answered so am guessing it is not possible to
create my wanted rule. Now am trying to solve it with virtual
datacenters in the crush map. Which works but maybe the the most
optimal solution.
On 2018-01-29 13:21, Wido den Hollander wrote:
On 01/29/2018 01:14 PM, Niklas wrote:
...
Is it your intention to put all copies of a object in only one DC?
What is your exact idea behind this rule? What's the purpose?
Wido
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