Hi all,
I'm trying to resolve a significant performance issue (not arbitrary dd
tests, etc but real users complaining, real workload performance).
I'm currently using 5 x 480GB SSD's in a RAID5 as follows:
md1 : active raid5 sdf1[0] sdc1[4] sdb1[5] sdd1[3] sde1[1]
1863535104 blocks super 1.2 level 5, 64k chunk, algorithm 2 [5/5]
[UUUUU]
bitmap: 4/4 pages [16KB], 65536KB chunk
Each drive only has a single partition, and is partitioned a little
smaller than the drive (supposedly this should improve performance).
Each drive is set to the deadline scheduler.
Drives are:
Intel 520s MLC 480G SATA3
Supposedly Read 550M/Write 520M
I think the workload being generated is simply too much for the
underlying drives. I've been collecting the information from
/sys/block/<drive>/stat every 10 seconds for each drive. What makes me
think the drives are overworked is that the backlog value gets very high
at the same time the users complain about performance.
The load is a bunch of windows VM's, which were working fine until
recently when I migrated the main fileserver/domain controller on
(previously it was a single SCSI Ultra320 disk on a standalone machine).
Hence, this also seems to indicate a lack of performance.
Currently the SSD's are connected to the onboard SATA ports (only SATA II):
00:1f.2 SATA controller: Intel Corporation Cougar Point 6 port SATA AHCI
Controller (rev 05)
There is one additional SSD which is just the OS drive also connected,
but it is mostly idle (all it does is log the stats/etc).
Assuming the issue is underlying hardware, then I'm thinking to do the
following:
1) Get a battery backed RAID controller card (which should improve
latency because the OS can pretend it is written while the card deals
with writing it to disk).
2) Move from a 5 disk RAID5 to a 8 disk RAID10, giving better data
protection (can lose up to four drives) and hopefully better performance
(main concern right now), and same capacity as current.
The real questions are:
1) Is this data enough to say that the performance issue is due to
underlying hardware as opposed to a mis-configuration?
2) If so, any suggestions on specific hardware which would help?
3) Would removing the bitmap make an improvement to the performance?
Motherboard is Intel S1200BTLR Serverboard - 6xSATAII / Raid 0,1,10,5
It is possibly to wipe the array and re-create that would help.......
Any comments, suggestions, advice greatly received.
Thanks,
Adam
--
Adam Goryachev
Website Managers
www.websitemanagers.com.au
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