[linux-lvm] cache on SSD makes system unresponsive
o1e9 at member.fsf.org
Sat Oct 21 14:10:36 UTC 2017
On 21. okt. 2017 04:55, Mike Snitzer wrote:
> On Thu, Oct 19 2017 at 5:59pm -0400,
> Oleg Cherkasov <o1e9 at member.fsf.org> wrote:
>> On 19. okt. 2017 21:09, John Stoffel wrote:
> So aside from SAR outout: you don't have any system logs? Or a vmcore
> of the system (assuming it crashed?) -- in it you could access the
> kernel log (via 'log' command in crash utility.
Unfortunately no logs. I have tried to see if I may recover dmesg
however no luck. All logs but the latest dmesg boot are zeroed. Of
course there are messages, secure and others however I do not see any
valuable information there.
System did not crash, OOM were going wind however I did manage to
Ctrl-Alt-Del from the main console via iLO so eventually it rebooted
with clean disk umount.
> More specifics on the workload would be useful. Also, more details on
> the LVM cache configuration (block size? writethrough or writeback?
No extra params but specifying mode writethrough initially. Hardware
RAID1 on cache disk is 64k and on main array hardware RAID5 128k.
I had followed precisely documentation from RHEL doc site so lvcreate,
lvconvert to update type and then lvconvert to add cache.
I have decided to try writeback after and shifted cachemode to it with
> I'll be looking very closely for any sign of memory leaks (both with
> code inspection and testing while kemmleak is enabled).
> But the more info you can provide on the workload the better.
According to SAR there are no records about 20min before I reboot, so I
suspect SAR daemon failed a victim of OOM.
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