Local RAM disk very slow

[DUOK]

Hi it's been a while since I've been around, and I haven't used VSAN for a while, but I have come up with a project in which it could be interesting to use it.

I have started to perform the basic configuration following the "Best Practices" and I find that with the performance tests in local, 1 single node, with a 100GB RAM disk, the performance is very bad.
I have tried with 3,4,5 ISCSI connections both in Loopback and local-to-local, also changing the MPIO from round-robin to least-queue-depth and I can't get the performance up.
The machine is 2xCPU Xeon 6242R with 384GB RAM DDR4-2933, Windows 2022 (I have also tried with W2019). Starwind v8.0.14398.
In sequential for RAM-Disk I see it low, but in random I see it worse.
I attach also the test of a local nvme disk on the same machine without Starwind.
The machine has no performance problems, bios in performance mode, no C-States P-States and all that....

I've done a thousand tests and nothing, I'm a little rusty.
What am I forgetting?

Starwind RAM disk iSCSI

Starwind01.png (76.16 KiB) Viewed 6551 times

Local nVME

Starwind02.png (92.76 KiB) Viewed 6546 times

[yaroslav (staff)]

RAM disk tests show the performance of the iSCSI stack.
For a lab, you can use StarWind NVMe-oF Target.
More readout https://www.starwindsoftware.com/resour ... r-fabrics/
https://www.starwindsoftware.com/resour ... ite-paper/
https://www.starwindsoftware.com/resour ... g-nvme-of/

[DUOK]

Hi Yaroslav

I'm sorry but I can't use NVMe-oF because the barebone servers are on a cloud provider (OVH) and I have to use a LACP team, so the RDMA is disabled.

My question is, can't iSCSI give more than this performance even if the performance of the substorage, in this case Ramdisk, is much higher?

[yaroslav (staff)]

Could you kindly tell me how many servers do you have connected to the RAM disk?
Once connected over iSCSI RAM disk shows the maximum possible performance over the iSCSI.

[DUOK]

Hi,
I am using a single local server. The RAM disk is on the same server from which I am making the connection(s).
My question is, is this the maximum speed you can get through iSCSI with a single server?

[yaroslav (staff)]

Hi,

Yes. iSCSI stack is often a bottleneck when we are talking about fast storage.
If you run any antivirus, try disabling it. To boost large blocks, try setting FirstBurstLenght to 262144 under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e97b-e325-11ce-bfc1-08002be10318}\000X\Parameters so it aligns with MaxBurstLength. Reboot is required.

[DUOK]

Hi Yaroslav,

I have already changed the registry key, I understand that 262144 in decimal, right?

Would I have to change also this parameter in Starwind?

Thanks.

[yaroslav (staff)]

Hi,

You need to modify the registry HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e97b-e325-11ce-bfc1-08002be10318}\000X\Parameters.

[DUOK]

Sorry Yaroslav.

I have already changed the registry value FirstBurstLenght in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e97b-e325-11ce-bfc1-08002be10318}\000X\Parameters

But two question, first, the number 262144 in decimal, right?

And second, should I also change the value First Burst Lenght (Default 65536) in the Starwind configuration?

[yaroslav (staff)]

Varying setting in StarWind VSAN may be not needed. Yes, this is a decimal value.