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Parity-Sync only 12.4MB/s on USB2.0 and SATA-II drives

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Here is what's going on with my array while parity-sync:


Total size:14 TB

Elapsed time:7 hours, 6 minutes

Current position:315 GB (2.3 %)

Estimated speed:12.4 MB/sec

Estimated finish: 12 days, 17 hours, 12 minutes



My use case is backing up photos (~1.5M files) and running PLEXSERVER. I had a mixed array of HDD on USB2.0 and SATA-II ports. They are SATA-III drives but pluggin in SATA-II on my HP Z800 workstation.


I had two questions (First time UNRAID user here so please bare with me):

1. What did I do wrong and why was the parity sync speed so slow? I did search in the forum, found some posts suggesting update CPU-C state to Always, but it didn't help either.

2. This HP Z800 board only SATA2 (3Gbps) and USB2.0, but it also had PCI-E 2.0 x16, should I get an HBA-i8 for these SATA-III drives and will it speed up the parity-sync?


Edited by tlk888
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3 minutes ago, tlk888 said:

Curious: USB2.0 specs is 480Mbps so I'd expect ~50-55MB/s in reality.

With overhead USB2 can only do 38-42MB/s at best. 

Then since parity operations require discs being in pretty tight sync there's likely some waits occurring due to buffering in various places.

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The good news: I moved USB2.0 disks to SATA3 and speed boosted. I saw 125MB/s on average and some time boosted to 611.8MB/s (!!!).


Current position:4.17 TB (29.8 %)

Estimated speed:605.6 MB/sec

Estimated finish:4 hours, 31 minutes


The bad news: It also introduced read errors and the drive (Disk 5, used to on USB.20) appeared as unmountable - it has data on it so I don't want to format.




So my question: how do I get the drive into the array without losing data? Thanks for being patient with me

Edited by tlk888
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The fact that the drive appears unmountable strongly suggests that the drive is not being presented exactly the same over SATA as it was over USB.  This is not an uncommon  occurrence.  If that is the case it will almost certainly be necessary to start with the disk outside the array, and copy the data onto the array after which the disk then can be added and formatted as Unraid likes to have it formatted.

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