Lot's of similar issues out there, I've been reading a lot of conversations on this and have not been able to pinpoint the issue. 

 

It was performing much better before, there's been some kind of change recently that has lead to a performance drop off. 

 

When writing to the disk array, transfer starts at 100mb and then drops down to 2mb, then up to 10mb, and down to 100k. It's somewhat erratic once it makes the drop. 

 

If I enable cache, it holds at 100mb without issue. This confirms that we're not dealing with a network issue. I've enabled reconstruct-write with no apparent improvement. Any suggestions in terms of what could be happening?

 

Hardware setup:

Thinkpad w/ i7, 8gb ram, USB 2 (I know, upgrading to USB 3 shortly...)

Mediasonic USB array with 4 x 8tb drives (one parity)

128GB SATA SSD Cache

 

 

 unraid-diagnostics-20220313-1421.zip

USB NOT recommended for array or pools

Is that right? Oh no, looks like I got some bad advice. Is there anything that I can do to try to resolve the current speed issues? Previously I had no problems doing 60mb sustained. 

Without parity you might be able to access a single disk in that enclosure at that speed. Once parity gets involved, multiple disks have to be accessed simultaneously.

  

3 hours ago, Kboogie said:

enabled reconstruct-write with no apparent improvement

That requires simultaneous access of ALL disks.

 

Lots of other problems can be expected depending on the implementation, such as

• inconsistent or non-unique identification of disks, which makes it impossible for Unraid to keep track of disk assignments
• non-standard disk sizes or partitions which may complicate disk replacement or moving disks to new hardware
• no SMART data so Unraid can't monitor disk health
• frequent disconnects which makes the array out-of-sync and require rebuilds.

Some people have good luck but we mostly hear about the bad luck on the forum. I usually say forget about parity for a USB array since without parity there isn't anything to keep in sync, and simultaneous disk access isn't required. Still could have some of those other issues though.