I'm planning to migrate an existing Filestore cluster with (SATA) SSD-based journals fronting multiple HDD-hosted OSDs - should be a common enough setup. So I've been trying to parse various contributions here and Ceph devs' blog posts (for which, thanks!) Seems the best way to repurpose that hardware would basically be to use those SSDs as DB partitions for Bluestore. The one thing I'm still wondering about is failure domains. With Filestore and SSD-backed journals, an SSD failure would kill writes but OSDs were otherwise still whole. Replacing the failed SSD quickly would get you back on your feet with relatively little data movement. Hence the question: what happens if a SSD that contains several partitions hosting DBs for multiple OSDs fails? Is OSDs data still recoverable upon replacing the SSD or is the entire lot basically toast? If so, might this warrant revisiting the old debate about RAID-1'ing SSDs in such as setup? Or I suppose at least not being too ambitious with the number of DBs hosted on a single SSD? Thoughts much appreciated! PS: It's not fully clear whether a separate WAL partition is useful in that setup? Sage posted about a month back: "[WAL] will always just spill over onto the next fastest device (wal -> db -> main)". I'll take that as meaning that a separate WAL partition would be counter-productive if hosted on the same SSD. Please correct me if I'm wrong? Cheers Christian _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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