[ceph-users] Hangs with qemu/libvirt/rbd when one host disappears

Christian Wuerdig christian.wuerdig at gmail.com
Thu Dec 7 17:17:16 PST 2017

On Thu, Dec 7, 2017 at 10:24 PM, Marcus Priesch <marcus at priesch.co.at> wrote:
> Hello Alwin, Dear All,


>> Mixing of spinners with SSDs is not recommended, as spinners will slow
>> down the pools residing on that root.
> why should this happen ? i would assume that osd's are seperate parts
> running on hosts - not influencing each other ?
> otherwise i would need a different set of hosts for the ssd's and the
> hdd's ?

You stated that you have one pool which uses SSD and HDD mixed with 3
replicas where 2 end up on SSD and 1 on HDD
Writes will not be ACKed untill all 3 replicas have been written as
such the slowest disk in the replica set determines the latency of the
write op
Reads can also be affected if you don't take care to ensure that
primary OSD for the set will always end up on an SSD - if you sift
through the archives there was a thread about this a while back


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