1

I plan to run esxi7 on Dell R640 Gen 10’s with Perc H740p/8gb mini mono controller, but am not sure of the speed difference between SATA-3 (6Gb/s) SSD - Crucial MX500 vs SAS-3 (10,000 RPM, 12Gb/s) HDD.

There would be 10 drives in a RAID5 config running around 25 virtual servers.
I am believe the SAS bus is way quicker than SATA, but the Sata SSD drives should be quicker than 10k SAS drives. Has anyone got this sort of setup and what has the better performance on say 60% read and 40% write?

5 Spice ups
2

In my lab (which admittedly doesn’t have a lot of active workloads going at once) I tend to get better latency over SATA SSDs, but I’m typically limited by the throughput of my storage controller (or network) before I utilize the full potential of any specific drive’s link speed.

I don’t have specific numbers for you, but just based on my own experience, I’d say a raid5 over 10 drives probably won’t make much difference either way, but the SATA drives might give you a slightly better latency on random reads/writes once (or IF) you saturate your controller’s cache.

3

SATA SSD over 15K and 10K SAS every day of the week for anything but high latency large block transfers. You are running more than 1 VM, so you need random IO from SSD. Period.

You shouldn’t run that many HDD in RAID 5 anyway. They should be in RAID 10 for performance and safety, at which point SATA SSD in RAID 5 can be faster and cheaper.

BTW, the 640 is a Dell 14th generation server.

4

I run 4way SATA SSD’s in RAID 5 and 8 way SAS mech drives in RAID 10 on my R740xd’s and it s no contest for I/O intensive the SSD’s are way faster. For large sequential R/W the SAS is marginally better after the cache on the H730 is filled but that only usually comes into play when backing up or moving VM’s.

5

Stop investing in spinning rust when dealing with virtualized servers. Get inexpensive read-intensive SSDs that fit your workload (TBW and DWPD parameters https://www.vmwareblog.org/shopping-ssds-several-tips-help-make-right-choice/ ) and call it a day. Do not purchase SSDs from DELL. That will cut your expenses by two at a minimum.