On Wed, Apr 22, 2015 at 4:30 PM, Nick Fisk <nick@xxxxxxxxxx> wrote: > I suspect you are hitting problems with sync writes, which Ceph isn't known > for being the fastest thing for. There's "not being the fastest thing" and "an expensive cluster of hardware that performs worse than a single SATA drive." :-( > I'm not a big expert on ZFS but I do know that a SSD ZIL is normally > recommended to allow fast sync writes. The VM already has an ZIL vdisk on an SSD on the KVM host. You may be thinking of NFS traffic, which is where ZFS and sync writes have such a long and difficult history. As far as I know, zfs receive operations do not do sync writes (except possibly at the beginning and end to establish barriers) since the operation as a whole already has fundamental transactionality built in. > SSD Ceph journals may give you around 200-300 iops SSD journals are not an option for this cluster. We just need to get the most out of what we have. There are some fio results showing this problem isn't limited/specific to ZFS which I will post in a separate message shortly. Thanks! _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
 |