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Slow transfer speed from HDD array to SSD pool

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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?


Edited by vichtorster
Added diagnostics
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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.

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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 by ahab666
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