Sudden drop in write performance for 4 x WD BLACK SN850X RAID5

[tethisIT]

Hi there,
we use 4 x WD Black SN850X 1 TB attached to an Intel RST Raid controller, configured as RAID5.
Asus ROG Maximus Z790 Dark Hero with Intel i9-14900K, Windows 11.

The write performance of that RAID was always at several GByte/s, read performance up to 20 GByte/s.
Those values are not close to the theoretical maximum, but that was to be expected. All good.

Now, all of a sudden, the write performance dropped drastically to around 750 MByte/s.

Why does that happen? One of those SSDs already had to be replaced on warranty, so we consider a drive problem as possible root cause.

Looking at the drives with Westen Digital Dashboard does show 8 to 10 % spare being used.
Anything else looks flawless, not temperatures exceeded, current firmware… I attache a few screenshots from WD Dashboard below.

Could the fact that spare is used at all cause such performance degradation?

Any other ideas what may cause this?
Any suggestion what to do?

Thanks a lot,
Christian

[karanamnagadurga.sai]

Hi @tethisIT

Have you checked our knowledge base articles?
(Get Support for Your SSDs and Flash Products | SanDisk)

Try this one.

• Common Causes and Solutions of Slow Data Backups and Transfer Speeds | SanDisk

Have you opened a Support Case?
If not, contact SanDisk Technical Support for assistance.
(Contact Support | SanDisk)

[tethisIT]

Hi Karanamnagadurga,
thanks for the response.
We are aware of the mentioned “common issues” and we checked if they indeed have an impact, but none of those factors was recently changed. So they do not explain the quite sudden drop to 10% of the previous performance.

And we did open a ticket, but for now it doesn’t get us anywhere. The SMART tests of those drives don’t report any errors and it would be VERY painful to remove the SSDs from the RAID to test them separately.

I’m trying to find out if someone experienced similar issues and found a solution…

Kind regards,

Christian

[crapdisk]

And now you have been ghosted. Terrific.

[Girofox]

Hello,

it seems you have a very old Intel VMD driver version from years (!) ago installed on your very new platform. There is already 20.2.4.1019 from 2025 out. The latest version is on Station-Drivers.
https://station-drivers.com/index.php/fr/component/remository/Drivers/Intel/Rapid-Storage-Technology-(RST)/Drivers/Intel-RST-20.x-Serie/Intel-Rapid-Storage-Technology-(RST-VMD)-Version-20.2.4.1019.4-WHQL/

I don’t have Raid but still have the VMD driver for my Sata drives. I recommened that you update your driver and test again.

[tethisIT]

Hi Girofox,

thanks for the input.
We already tried different versions of the driver including the newest one.
But that doesn’t change anything.

Cheers,
Christian

[Vegan]

consumer M.2 NVMe are not designed for RAID. That is in server shops where aggregate storage is used widely.