Slow transfer speed from HDD array to SSD pool

[vichtorster]

Transfers speed starts at what is to be expected from my HDD in the array (120 MB/s) but than slow down to 30 MB/s and stay at that speed for the rest of the data transfer.

Also copying between separate SSD pools behaves in this way. Starts at 400 MB/s and after 20 gigabytes copied the transfer stays at 22 MB/s.

This behavior is observed with docker/VMs enabled and disabled. 

I have already tried TRIM.

Any ideas what causes this?

norad9-diagnostics-20240118-0739.zip

Edited January 18 by vichtorster
Added diagnostics

[Kilrah]

Probably those low-end SSDs, seems sub-50MB/s on extended writes that have filled the pSLC cache isn't surprising. 

 

https://goughlui.com/2023/03/11/review-patriot-burst-elite-1-92tb-2-5-sata-iii-ssd-pbe192ts25ssdr/

Edited January 18 by Kilrah

[vichtorster]

Thanks for the reply. I did replace my older smaller SSDs with these cheap Patriots at some point. Now that I think about it this might actually be when I started noticing these issues. I have to admit I have underestimated the how cheap these cheap SSDs can be.

[ahab666]

Well, I am facing a similar problem even with only one HQ (???) nvme as cache drive ....

 

The moving of the files from a defective drive (emulated by one parity) drive runs with 30 to 95 MB/sec and uses up to 60% CPU resources.

So moving a half full 18 TB drive seems to take 4 ever - reading speed off the HDD are about 140 MB/sec, writing speeds are around 80-90 ...

Transfer speeds stay at about 100 for some short time (20 sec) and then crash down to 20 or 30 for the next few minuts ..... so patience ....

 

I just hope that the emulated date stay emulated until a crc 32 as well as some MD5 hash check confirm the validity of the data on the physical drive ... 

 

good luck to you and cheers

Edited January 18 by ahab666
correction