[ClusterLabs] DRBD and SSD TRIM - Slow!

[Eric Robinson]

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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