Hi all,

 

I have the following drives on my Windows VM on my nvme cache drive.

1. C:// - vdisk

[Read] Sequential 1MiB (Q=  8, T= 1): 13017.156 MB/s [  12414.1 IOPS] <   642.75 us>

[Write] Sequential 1MiB (Q=  8, T= 1):  3745.290 MB/s [   3571.8 IOPS] <  2224.04 us>
 

2. Y:// - ssd share
[Read] Sequential 1MiB (Q=  8, T= 1):  3045.652 MB/s [   2904.6 IOPS] <  2736.75 us>

[Write] Sequential 1MiB (Q=  8, T= 1):   482.934 MB/s [    460.6 IOPS] < 17330.33 us>

 

3 Z:// - nvme share

[Read] Sequential 1MiB (Q=  8, T= 1):  3186.777 MB/s [   3039.1 IOPS] <  2629.13 us>

[Write] Sequential 1MiB (Q=  8, T= 1):  1201.488 MB/s [   1145.8 IOPS] <  6964.21 us>

 

Unfortunately, as you can see above, I'm getting almost the same read performance on my nvme as if it were a normal ssd. I was hoping speeds close to the C drive as they are technically on the same nvme drive.

 

Can anyone care to explain what's going on and how I can remedy this?

 

Thanks 

Edited April 15, 20206 yr by rjbernaldo

Your testing method is flawed.

 

Data looks to certainly have been cached in RAM for your read test.

There's no way "normal SSD" (by that I think you meant SATA SSD) can get 3045.652 MB/s (that is 3 gigabytes per second). Max throughput for SATA isn't anywhere near that speed.

Similarly, your vdisk 13 GB/s is faster than any PCIe x4 NVMe drive can get, even PCIe 4.0.

 

Write speed is probably a better indication.

482 MB/s for SATA and 1.2 GB/s for NVMe sound about right.

3 GB/s vdisk performance probably is VM itself is caching write in RAM.

 

So TL;DR: nothing to remedy.

@testdasi Ah, right. Would it make a different if I move some heavy programs to the vdisk versus keeping it in the nvme share?

7 hours ago, rjbernaldo said:

@testdasi Ah, right. Would it make a different if I move some heavy programs to the vdisk versus keeping it in the nvme share?

The answer is unfortunately "it depends". What sort of things are you looking to move?

Generally anything that does a lot of random IO will benefit more. But then it depends on how much IO is done too so the benefit may not be perceptible.

18 hours ago, testdasi said:

The answer is unfortunately "it depends". What sort of things are you looking to move?

Generally anything that does a lot of random IO will benefit more. But then it depends on how much IO is done too so the benefit may not be perceptible.

Mostly just steam games and unity. Would that be of enough benefit to warrant an additional vdisk?

No. Game storage would be fine on network drive. VM on the same server accesses network with virtual 100Gbps adapter so there's no bottleneck. Latency is a bit high but for loading games, they rarely ever matter.