ESXI 6.7 slow disk speed on Dell R410

I’m running my Dell R410 with a SAS 6i/r HBA with a Seagate Constellation ES 2TB SAS Hard drive and I’m having really slow disk performance (10mb/s max) with latency of 40ms and above on both transfers using WinSCP and creating and installing VM’s (note those tests no other VM’s were running).

I am using Dell EMC’s ESXI 6.7U3 image and I recently upgraded from 6.5 because I had the same problem. Am I missing a driver that is slowing me down? If so what one do I need?

It can’t be the disk as I had a pair of Raid 0 160GB Hard drives (not the fastest) and that too was only reaching 10mb/s. I also had an SSD in the system but that would only reach 30mb/s with latency of about 70ms+ so that too was slow.

Any ideas welcome, I’m stumped.

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One Comment

  1. you will want to examine the sas controllers read/write cache settings; without a cache battery backup unit, and sometimes even with a battery back up unit installed, the controller may default to “write through“ mode. This implies then that all writes and reads to and from the storage media are done synchronously, which are far slower than asynchronous operations.

    One can manually force the cache to “write back“ mode. this will probably resolve the performance issue you’re describing.

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