On 06/13/2018 11:39 AM, Chris Dunlop wrote:
> Hi,
>
> Is the osd journal flushed completely on a clean shutdown?
>
> In this case, with Jewel, and FileStore osds, and a "clean shutdown" being:
>
It is, a Jewel OSD will flush it's journal on a clean shutdown. The
flush-journal is no longer needed.
Wido
> systemctl stop ceph-osd@${osd}
>
> I understand it's documented practice to issue a --flush-journal after
> shutting down down an osd if you're intending to do anything with the
> journal, but herein lies the sorry tale...
>
> I've accidentally issued a 'blkdiscard' on a whole SSD device containing
> the journals for multiple osds, rather than for a specific partition as
> intended.
>
> The affected osds themselves continue to work along happily.
>
> I assume the journals are write-only during normal operation, in which
> case it's understandable the osds are oblivious to the underlying
> zeroing of the journals (and partition table!).
>
> The GPT partition table and the individual journal partition types and
> guids etc. have been recreated, so, in theory at least, a clean shutdown
> and restart should be fine *if* the clean shutdown means there's nothing
> in the journal to replay on startup.
>
> I've experimented with one of the affected osds (used for "scatch"
> purposes, so safe to play with), shutting it down and starting it up
> again, and it seems to be happy - somewhat to my surprise. I thought I'd
> have to at least use --mkjournal before it would start up again, to
> reinstate whatever header/signature is used in the journals.
>
> There are other affected osds which hold live data, so I want to be more
> careful there.
>
> One option is to simply kill the affected osds and recreate them, and
> allow the data redundancy to take care of things.
>
> However I'm wondering if things should theoretically be ok if I
> carefully shutdown and restart each of the remaining osds in turn, or am
> I taking some kind of data corruption risk?
>
> Tks,
>
> Chris
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