SOLVED SAS resilver slower than SATA resilver

[sfanla]

Hello, I just bought a lot of 15 HGST 8TB SAS HDD HUH728080AL420 from 2016. They are helium drives, pre WD acquisition (I think). From what I understand, all drives pre 2017 from that line were always CMR. For some reason my resilvering on drive replacements with these is multiple times slower than the WD SATA 8TB RED PLUS. It's not done yet so I don't know how long it will take total, but it's at LEAST 400% longer to replace my 2TB with one of these SAS drives than it was to replace my 2TB in the array with a SATA one.

I started off all 2TB SSDs, they were full to about 84% each. I replaced 9 of them using the WD RED SATA drives, and it took almost exactly 5.5h per drive. That was very stable, to the point I was starting to think "great, rule of thumb is make sure I plan 3h per TB and I should be peachy". But these HGST drives which are supposedly faster (7200 RPM as opposed to 5400 RPM), in the exact same pool, replacing the exact same drives in the VDEVs are taking more like 10-12h per TB. I am really confused.

Thanks

 

[sfanla]

shoot. Mods, I put this in Core, can it please be moved to Scale?

 

[sfanla]

Okay, I found the issue. The SAS drives were used in a configuration where their cache was turned off previously and this carried over. I used

to check the state
smartctl -g wcache /dev/sdw
and to enable it
smartctl -s wcache,on /dev/sdw

Nothing, reboot, fixed! As you can see the writes are now at a reasonable speed.