Hi.
I have 4 SSD drives of SD Ultra 3D 2TB with FW 530500WD. I use them inside my small home server.
However, in my first setup, I was using ZFS raidz10 which worked well. Because of some issues, I had to rebuilt my whole system. I got a HPE SmartArray E208 card which I wanted to try. So I installed it and created a new config.
I noticed, that this card actively metioned, that it will disable the write cache of a configured device. Well, okay, go on.
After another issue, I removed this card from the system, reset it and connected all ssds back to the internal SATA controller.
I set up a new system without the card, just the drives and the internal SATA AHCI Controller.
I noticed huge performance issues with the drives and after some tests:
dmesg: Write cache: disabled, read cache: enabled, doesn’t support DPO or FUA
smartctl: Write cache is: Disabled
I asked my AI about this and it gave me a clear result: WCE-Flag (Write Cache enabled) inside the SSD seems to be set to OFF. And the AI states, it cant be enabled.
Well. I dont know if WCE was never enabled inside these drives (some SanDisk support agent here?).
Enabling the cache with hdparm -W1 can enable it, but it doesnt last any reboot.
Anyone with some experience here? Is the drive cache disabled by default within the firmware? If yes, can it be enabled by default? Is it possible by some command to permanently disable an enabled WCE-Flag (like I think the HPE Array card has done)?
AI said the only way to enable it, is a udev rule inside my linux. But I never heard, that a SSD write cache has to be manually enabled.
Thanks in advance!
