About IOPS of a RAID5 disk array without cache
we are using a 530-8i RAID adapter,which is none-cache supported, on a Lenovo ThinkSystem SR590 server.And we have 4 HDD(600GB/10K RPM/SAS) in the array. I read an article about calculating the disk/disk array IOPS,our disk array should get IOPS like 130 ,theoretically. I did a test with a tool called CrystalDiskMark,but can only get about 20 IOPS when doing SEQ1M write test. Is this a normal performance of a raid adpter without cache?If not,how can I improve the performance?
The output from CrystalDiskMark:
- MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
- KB = 1000 bytes, KiB = 1024 bytes
[Read] SEQ 1MiB (Q= 8, T= 1): 521.796 MB/s [ 497.6 IOPS] < 16036.35 us>
SEQ 1MiB (Q= 1, T= 1): 466.978 MB/s [ 445.3 IOPS] < 2242.63 us>
RND 4KiB (Q= 32, T= 1): 9.169 MB/s [ 2238.5 IOPS] < 14248.25 us>
RND 4KiB (Q= 1, T= 1): 1.219 MB/s [ 297.6 IOPS] < 3352.98 us>
[Write]
SEQ 1MiB (Q= 8, T= 1): 23.278 MB/s [ 22.2 IOPS] <346183.31 us>
SEQ 1MiB (Q= 1, T= 1): 20.761 MB/s [ 19.8 IOPS] < 50402.19 us>
RND 4KiB (Q= 32, T= 1): 2.203 MB/s [ 537.8 IOPS] < 58681.18 us>
RND 4KiB (Q= 1, T= 1): 0.751 MB/s [ 183.3 IOPS] < 5439.00 us>
Profile: Default Test: 1 GiB (x3) [D: 0% (5/1574GiB)] Mode: [Admin] Time: Measure 5 sec / Interval 5 sec Date: 2021/01/26 14:28:39 OS: Windows Server 2012 R2 Server Standard (full installation) [6.3 Build 9600] (x64)
The article about calculating IOPS I read: https://ryanfrantz.com/posts/calculating-disk-iops.html
The information of ThinkSystem 530-8i RAID adapter: https://lenovopress.com/lp0651-thinksystem-raid-530-series-internal-raid-adapters
This is a quite common behavior of memory-less HW RAID controller. Basically, the main issue is that without a temporary, safe DRAM cache, writes can not be coalesced, leading to frequent read/modify/write cycles. This is exacerbated by the RAID card disabling HDD own cache.
I suggest you to either use a proper, powerloss-protected RAID card, or to use plain mirroring.
You can read more here.