[ClusterLabs] Antw: DRBD and SSD TRIM - Slow!

[Eric Robinson]

1) iotop did not show any significant io, just maybe 30k/second of drbd traffic.

2) okay. I've never done that before. I'll give it a shot.

3) I'm not sure what I'm looking at there.

--
Eric Robinson

> -----Original Message-----
> From: Ulrich Windl [mailto:Ulrich.Windl at rz.uni-regensburg.de]
> Sent: Tuesday, August 01, 2017 11:28 PM
> To: users at clusterlabs.org
> Subject: [ClusterLabs] Antw: DRBD and SSD TRIM - Slow!
> 
> Hi!
> 
> I know little about trim operations, but you could try one of these:
> 
> 1) iotop to see whether some I/O is done during trimming (assuming
> trimming itself is not considered to be I/O)
> 
> 2) Try blocktrace on the affected devices to see what's going on. It's hard to
> set up and to extract the info you are looking for, but it provides deep
> insights
> 
> 3) Watch /sys/block/$BDEV/stat for performance statistics. I don't know how
> well DRBD supports these, however (e.g. MDRAID shows no wait times and
> no busy operations, while a multipath map has it all).
> 
> Regards,
> Ulrich
> 
> >>> Eric Robinson <eric.robinson at psmnv.com> schrieb am 02.08.2017 um
> >>> 07:09 in
> Nachricht
> <DM5PR03MB27297014DF96DC01FE849A63FAB00 at DM5PR03MB2729.nampr
> d03.prod.outlook.com>
> 
> > Does anyone know why trimming a filesystem mounted on a DRBD volume
> > takes so long? I mean like three days to trim a 1.2TB filesystem.
> >
> > Here are some pertinent details:
> >
> > OS: SLES 12 SP2
> > Kernel: 4.4.74-92.29
> > Drives: 6 x Samsung SSD 840 Pro 512GB
> > RAID: 0 (mdraid)
> > DRBD: 9.0.8
> > Protocol: C
> > Network: Gigabit
> > Utilization: 10%
> > Latency: < 1ms
> > Loss: 0%
> > Iperf test: 900 mbits/sec
> >
> > When I write to a non-DRBD partition, I get 400MB/sec (bypassing caches).
> > When I trim a non-DRBD partition, it completes fast.
> > When I write to a DRBD volume, I get 80MB/sec.
> >
> > When I trim a DRBD volume, it takes bloody ages!
> >
> > --
> > Eric Robinson
> 
> 
> 
> 
> 
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