slow sync performance on LSI / Broadcom MegaRaid performance with battery cache
From: Stefan Priebe - Profihost AG
Date: Wed Jan 08 2020 - 02:03:45 EST
Hello list,
while we used adaptec controller with battery cache for years we
recently switched to dell hw using the perc controllers which are
rebranded lsi/broadcom controllers.
We're running btrfs subvolume / snapshot workloads and while those are
very fast on btrfs using a btrfs raid 0 on top of several raid 5 running
on adaptec (battery backed up) in write back mode.
The performance really sucks on those LSI controllers even the one i
have has 8GB cache instead of just 1GB at adaptec.
Especially sync / fsync are awfully slow taking sometimes 30-45 minutes
while btrfs is doing snapshots. The workload on all machines is the same
and the disks are ok.
Is there a way to disable FLUSH / sync at all for those devices? Just to
test?
I'm already using nobarrier mount option on btrfs but this does not help
either.
Thanks!
Greets,
Stefan