High Latency with SSD drive?

[VinceStrem]

The server that I am seeing this issue is a HP Dl360Gen9.   It came with a P440AR controller where I have 2 drives connected to it,  Each is set up as RAID 0 its own.  I set it up this way because when I did not configure it as RAID 0, I can not see the drive in ESX.  The first drive is used as a datastore for local ISO file.  Not too concern about that one.  The 2nd drive is a Samsung 850EVO 256GB SSD drive that I am using as a Local datastore for use as Host Cache.  When I look at the write latency under the performance tab, Storage path,  it is averying 9.9 or 10 millisecond.  All my other drives are under 1 ms.

Using ESXTOP,  I am getting 10-12 in the DAVG/cmd.

Is this normal?

Thanks

Vince

[brunofernandez1]

Hi Vince

About configuring the disks as raid 0 is normal for hp raud controllers. they are only recognized when you create a logical disk on the controller...

and now to your actual problem. is there allready someting runing on the disk?

i would say up to 10ms latency is normal if there is allready something using the disk...

[VinceStrem]

Hi Bruno,

Not sure what you mean by something running on the disk.  The only thing this datastore is used for is for host cache. 

Vince

[brunofernandez1]

i was asking if the host is allready writing/caching something to the disk?

[VinceStrem]

Nope, nothing else besides the caching.

[brunofernandez1]

i thought samsung was having problems with so 850er firmware...could this be related to your problem?

[Duncan Epping]

caching as in "vSphere Flash Read Cache"? Cause if you are referring to swap on SSD then there isn't likely anything happening right now, unless you are memory overcommitted.