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incredibly slow parity

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just fired up my Unraid with 20 TB Exos disks. Started Parity. Two things I noticed:

  • The parity disks (which are in another enclosure) started off with tons (thousands) of UDMA CRC errors. Currently things are quiet. Might be cabling issue. I am unsure yet.
  • The parity buildup is INCREDIBLY slow (10 MB/sec) and will take like a month. 


I am in the background syncing my old NAS with rsync streams to the Unraid server. So my assumption is that due to the random writes the parity is so slow. Is this feasible? Or am I looking at something else and need to investigate?




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  • Solution

Hi Jonathan,


Supermicro 36bay enclosure with two Expanders. Each connected to a port on the internal LSI 16i.


After I stopped the writes it seems to speed up to 270MB/sec which is the maximum I would have expected. Will let it finish now and start the writes then. Moreover my two NVMes for the pool arrive tomorrow. So new day new luck.

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