Question Supermicro LSI 3108 RAID controller slow write speed.

Mar 26, 2021
Hi All,

I have a Supermicro X10DRL-C server with LSI 3018 RAID controller.

ESXi 6.7 U2 runs on this server.
8 * 500 GB SATA SSD present on this server.
Created RAID 10 and connected all the 8 * 500 GB SATA SSD connected in to RAID 10.

3 MAC VMs are running on ESXi OS.

When I check the disk speed from MACOS,I see the following.

Read speed is 1025 MB/s
Write speed is 338.5 MB/s.

As this is LSI 3018 RAID will provide 12 GB/s and the connected SATA cable speed with SATA SSD is 6 GB/s


Why Im getting the slow write speed?
I should get alteast more than 1000 MB/s ?
As this is ESXi,Can I install megaraid vib with fast path enabled to improve write performance?

How to improve the write speed?

Thank you,
It is normal, you write data to 4 hdds at once but you can read from 8 hdds. This is how RAID 10 works. 4x130 MB/s is 520 MB/s at writing, 8x150 MB/s is 1200 MB/s at reading, it seems pretty normal to me. Take in consideration that the VM enviroment will have some overhead and you will not get max speeds.
Mar 26, 2021
Thanks Dragos for your explanation. I understood.
Im using the "Samsung ssd 850 evo 500gb". As per the specification,it can give max 520 MBps write speed and the read speed is 540 MBps .
  • 540 MBps (read) / 520 MBps (write)
As per the specs calculation, It means, write speed 4 SSD * 520 MBps = 2080 MBps and the read speed is 8 * 540 MBps = 4320 MBps.

However,atleast half of the write speed i should get 1040 mbps.

Am I understanding correct?