Disk Speed performance for SSD HW RAID-10 and Controller Cache Policy

Umair

Hi Guys,

I am in the process of setting up a new server and was hoping to get some input from the community. The new server is being setup with 4 1TB SSDs in HW RAID 10.

I am getting high 4K read/write speeds with RWTD but all other's (64k, 512k,1m) are almost half. With RWBD, 4K /read/write speed suffers a little but everything else (64k, 512k,1m) seems better. (Strip size if 64 KB)

RWBD

Block Size | 4k            (IOPS) | 64k           (IOPS)
  ------   | ---            ----  | ----           ----
Read       | 101.14 MB/s  (25.2k) | 1.39 GB/s    (21.8k)
Write      | 101.41 MB/s  (25.3k) | 1.40 GB/s    (21.9k)
Total      | 202.55 MB/s  (50.6k) | 2.79 GB/s    (43.7k)
           |                      |
Block Size | 512k          (IOPS) | 1m            (IOPS)
  ------   | ---            ----  | ----           ----
Read       | 1.51 GB/s     (2.9k) | 1.37 GB/s     (1.3k)
Write      | 1.59 GB/s     (3.1k) | 1.46 GB/s     (1.4k)
Total      | 3.10 GB/s     (6.0k) | 2.83 GB/s     (2.7k) 

And RWTD

Block Size | 4k            (IOPS) | 64k           (IOPS)
  ------   | ---            ----  | ----           ----
Read       | 242.37 MB/s  (60.5k) | 598.29 MB/s   (9.3k)
Write      | 243.01 MB/s  (60.7k) | 601.44 MB/s   (9.3k)
Total      | 485.39 MB/s (121.3k) | 1.19 GB/s    (18.7k)
           |                      |
Block Size | 512k          (IOPS) | 1m            (IOPS)
  ------   | ---            ----  | ----           ----
Read       | 585.18 MB/s   (1.1k) | 582.87 MB/s    (569)
Write      | 616.27 MB/s   (1.2k) | 621.69 MB/s    (607)
Total      | 1.20 GB/s     (2.3k) | 1.20 GB/s     (1.1k)

So any suggestions / comments ?? Reading up with lot of info, it is recommended to use WB cache.

The controller is LSI 3108 and does have BBU.

Also do you think these speed/IOs are decent enough for SSD RAID 10??
Which controller Cache policy would you recommend ?? (And Also the strip size)

As for my usage case, this will be a KVM node running a bunch of VMs. (few DB intensive VMs and few high traffic WP sites).

Thanks a lot

Umair

No one ?

In real usage (i.e. not the bench mark script), a WordPress website with lots of files and images, should I just focus on 4k performance and ignore 64k/512k??

Any suggestions / comments ??