Question Supermicro LSI 3108 RAID controller slow write speed.

Mar 26, 2021
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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 controller.it will provide 12 GB/s and the connected SATA cable speed with SATA SSD is 6 GB/s

Question?

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,
Raj
 
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
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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?
 

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