On Mon, Jan 29, 2018 at 9:37 AM Vladimir Prokofev <v@xxxxxxxxxxx> wrote:
Hello.In short: what are the consequence of loosing external WAL/DB device(assuming it’s SSD) in bluestore?In comparison with filestore - we used to have an external SSD for journaling multiple HDD OSDs. Hardware failure of such a device would not be that big of a deal, as we can quickly use xfs_repair to initialize a new journal. You don't have to redeploy OSDs, just provide them with a new journal device, remount XFS, and restart osd process so it can quickly update its state. Healthy state can be restored in a matter of minutes.That was with filestore.Now what's the situation with bluestore?What will happen in different scenarios. like having only WAL on external device, or DB, or both WAL+DB?I kind of assume that loosing DB means losing OSD, and it has to be redeployed?
I'll let the BlueStore guys speak to this more directly, but I believe you lose the OSD.
However, let's be clear: this is not really a different situation than with FileStore. You *can* with FileStore fix the xfs filesystem and persuade the OSD to start up again by giving it a new journal. But this is a *lie* to the OSD about the state of its data and is very likely to introduce data loss or inconsistencies. You shouldn't do it unless the OSD hosts the only copy of a PG in your cluster.
-Greg
_______________________________________________What about WAL? Any specific commands to restore it, similar to xfs_repair?I didn't find any docs regarding this matter, but maybe I'm doing it badly, so a link to such doc would be great.
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