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Very slow data transfer speeds

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Hi,

I have been replacing some hard drives. With parity checks and when rebuilding the replacement hard drives, the speeds were in line with what I’m used to at around 130-175 MB/s

 

But after the replacement HDDs were in, I have been converting to ZFS so have been using Unbalanced to empty drives so I can convert each empty drive to ZFS without losing any data. The problem is when I move data from one drive to the other, whether directly or using Unbalanced, the transfer rates are very slow at around 20-25 MB/s.

 

Is this normal?  Why such the discrepancy between file transfers vs data rebuilds/parity checks?  I’m assuming I have something configured wrong, but I can’t figure out what it might be.

 

Also, after some of these long multi-day file transfers and after some data rebuilds, I can no longer stop the array.  The only thing it will let me do is restart the server with the Unraid WebUI, but when it comes back up, it complains about unclean shutdown and has to do a parity check.  Parity has never found a problem when this happens, but I would like to know why I cannot stop the array in these situations.


Thanks!

server-diagnostics-20250115-0121.zip

  • Community Expert

Array to array transfers are always slow, because of parity getting updated and turbo write cannot be used, also note that presently, zfs has a known performance issue with writes, when used in the array only.

  • Author

Ok, so this is expected behavior then. I can accept that as this is a one-time event as I convert.  Any idea why I can't stop the array after the transfers/Unbalanced is finished?

  • Community Expert

You may need to wait a couple of minutes for the RAM to be flushed, it's it more than that, there's likely something preventing the disks from unmounting, if it's just after using the plugin, recommend asking in the plugin support thread.

  • Community Expert
29 minutes ago, Aquenon said:

 Any idea why I can't stop the array after the transfers/Unbalanced is finished?

Make sure you don't have a rogue file open or a terminal window open browsing the array. It will prevent the disk you're accessing from un-mounting.

Edited by MowMdown

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