Disk Performance for SSD HW RAID-10 and Controller Cache Policy

[LoterGarry]

Hi Everyone,

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 but everything else (64k, 512k,1m) seems better. (Strip size if 64 KB). The test is done using YABS. (But I am doing multiple different tests and the results are similar.

RWBD

PHP Code:
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

PHP Code:
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

[JasonByrne]

"Probably if you search enough, the recommendation will be to turn off write cache of controller for SSD with your controller.
The reason is SSDs are very fast."

[DaneShayd]

Drive maintenance is crucial for performance. I rely on hdd format for secure erases, which keeps drives stable. For cache policy, write-back likely offers better throughput but watch for degradation.