Slow seq read on pm1725a (dell)

[Rand__]

After I got my Dell PM1725a's flashed to the latest FW I now begun the replacement process in my ZFS filer.
I am looking to replace 12 SS300 SAS3 SSDs with 2 pairs of 1725a 3.2 TB - basically a small size increase paired with a small theoretical performance increase (non scaling activities ie single mirror usage due to single user).

However, the PM1725a do have a very weird issue with seq read speeds (only). See the following comparison (CDM) from a nfs attached VM betwwen the SS300 and the PM172a's (same box,slightly different ZFS settings but that should not amount for that huge difference).

Anyone a clue what might be up perhaps before I dive into the abyss of performance issue debugging?

SS300 (6 pairs)


PM1725a (single pair)



Thanks

 

[Whaaat]

If you are testing CDM, then it is clear that version 5 fails on 4k q1 writes and version 7 fails on sequential read with samsung. Any real world test like copying files to/from this volume?

 

[Rand__]

Hm... some further experiments on another box with the other 2 drives.
Directly attached to mainboard via onboard Occulink port, Windows 2012, nothing else running

Totally inconsistent behavior... (runs are consecutively)

Run 1


Run 2


Run 3





No, have not done any real life tests to be honest, will move some VMs over later today and report