L2 (Optane) R/W L1 100%R, Writes are too fast for RO!
Posted: Fri Jun 11, 2021 11:49 am
Hello,
as a new (trial) User I might get something wrong, but I am really confused:
Preface:
A VM (on proper Hardware & ESXi) has some unoptimized (closed source) code I cannot alter.
So the idea is to improve (un)snappiness with Optane (900p) with PCIe passthrough.
The default SSD (Raid 1, 2 SATA drives) shall be accelerated (mostly in terms of latency, hence Optane).
Set 900p as L2, Enable write defer 1s, Write mode: Average
(should be "reasonable" in terms of data integrity, I think(?))
CrystalDiskMark "Real World Performance + Mix" now shows numbers for main drive as if it was Optane, that's what I've expexted / hoped!
Now to my quesion:
Adding 4096MB of L1 with 100% read now also accelerates writes (7µs RND4K!)
That I didn't expect, and don't wanna have (in terms of data integrity?)
Also, the "Total Write L1" increases on write operations?
I first thought: Yeah, that's supposed to happen, as the read-cache needs to be filled, but then again, why does the write-speed latency drops below capabilities of Optane?
Is PrimoCache too "smart" for CrystalDiskMark, or what am I missing?
Grateful for any hint in the right direction (or the correct search terms)!
Yours, Mecky
as a new (trial) User I might get something wrong, but I am really confused:
Preface:
A VM (on proper Hardware & ESXi) has some unoptimized (closed source) code I cannot alter.
So the idea is to improve (un)snappiness with Optane (900p) with PCIe passthrough.
The default SSD (Raid 1, 2 SATA drives) shall be accelerated (mostly in terms of latency, hence Optane).
Set 900p as L2, Enable write defer 1s, Write mode: Average
(should be "reasonable" in terms of data integrity, I think(?))
CrystalDiskMark "Real World Performance + Mix" now shows numbers for main drive as if it was Optane, that's what I've expexted / hoped!
Now to my quesion:
Adding 4096MB of L1 with 100% read now also accelerates writes (7µs RND4K!)
That I didn't expect, and don't wanna have (in terms of data integrity?)
Also, the "Total Write L1" increases on write operations?
I first thought: Yeah, that's supposed to happen, as the read-cache needs to be filled, but then again, why does the write-speed latency drops below capabilities of Optane?
Is PrimoCache too "smart" for CrystalDiskMark, or what am I missing?
Grateful for any hint in the right direction (or the correct search terms)!
Yours, Mecky