You referenced parallel writes for journal and data. Which is default for btrfs but but XFS. Now you are mentioning multiple parallel writes to the drive , which of course yes will occur.
Also Our Dell 400 Gb NVMe drives do not top out around 5-7 sequential writes as you mentioned. That would be 5-7 random writes from a drives perspective and the NVMe drives can do many times that. I would park it at 5-6 partitions per NVMe , journal on the same disk. Frequently I want more concurrent operations , rather than all out throughput. On Thu, Feb 4, 2016 at 6:49 AM Sascha Vogt <sascha.v...@gmail.com> wrote: > Am 03.02.2016 um 17:24 schrieb Wade Holler: > > AFAIK when using XFS, parallel write as you described is not enabled. > Not sure I'm getting this. If I have multiple OSDs on the same NVMe > (separated by different data-partitions) I have multiple parallel writes > (one "stream" per OSD), or am I mistaken? > > > Regardless in a way though the NVMe drives are so fast it shouldn't > > matter much the partitioned journal or other choice. > Thanks, does anyone has benchmarks on this. How about the size of the > journal? > > > What I would be more interested in is you replication size on the cache > > pool. > > > > This might sound crazy but if your KVM instances are really that short > > lived, could you get away with size=2 on the cache pool from and > > availability perspective ? > :) We are already on min_size=1, size=2 - we even ran for a while witz > min_size=1, size=1, so we cannot squeeze out much more on that end. > > Greetings > -Sascha- > > PS: Thanks a lot already for all the answers! > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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