When it rains, it pours.
Zitat von "Jens-U. Mozdzen" <[email protected]>:
Zitat von "Jens-U. Mozdzen" <[email protected]>:
Hi everybody,
we experience reproducible server crashes (reboots) when creating
new file systems on bcache'd devices.
update: If I set cache_mode to "writethrough", I can successfully
create the file system.
over the weekend, I received multiple successive reports about disks
failing in the RAID, on both servers. This is a rather new hardware
setup, no disk is older than 6 months, so I didn't actually believe in
failing disks to be the reason.
In syslog I noticed reports from the upper layers (SCST, which is
using files on the ext4->DRBD->LVM->bcache->MD-RAID chain) indicating
stalling disk access; DRBD reporting stalling updates from the remote
server), both indicating some kind of locking condition inside the
kernel. The RAID failures were right after these incidents.
With identical workload, but having turned caching back to
"writeback", no more "RAID failures" were reported.
We received end-user reports that system access sometimes hangs for a
few seconds, which now makes me believe that the actual cause lies
somewhere within the software stack on our servers, most probably
within the bcache layer (as no such problems were reported before
introducing bcache to our setup).
Is there anyone out there that is running bcache on MD-RAIDs (both for
data and cache device) with significant I/O volume, successfully? I'd
like to compare setups then :)
Regards,
Jens
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