Was trying to upgrade some of my WD 2TB Reds with 8TB Reds and have noticed very slow read speeds. Write speeds saturate my gigabit connection like I would expect. Read speeds will typically hover around 55 MB/s. I have tried multiple cat6 cables, different ports on my switch, internal motherboard SATA rather than external SAS and the problem persists. The weird part is if I transfer from a 2TB Red, the read speeds go back to saturating the link. So it appears to be specific to these 8TB disks and unRAID. I know a lot of peeps here use them so I'm assuming I have missed a simple setting somewhere.

 

I forgot to grab the diagnostics from earlier when I had multiple disks in the system, both 2TB and 8TB Reds so I put one back in, rebooted and ran a transfer, then grabbed the diagnostics. This transfer was better but typically hovered very low. 

 

Pay no attention to the UDMA CDC errors on this drive. That was from a different test and apparently my SAS cards (SAS9201-16e) do not like these drives at all. Within minutes some of my drives had in excess of 400 UDMA errors. So the diagnostics attached is with a 8TB Red running off my onboard SATA ports.

 

edit: I should also mentioned I put this exact disk into my Windows machine and it transfers internally at 180 MB/s or so and across the network at 112 MB/s. So I honestly didn't feel it was a disk issue.

 

bkp003-diagnostics-20170315-1952.zip

Edited March 16, 20179 yr by CyberSkulls

See if this helps:

 

 

Gave that a try. Also rebooted the unRAID server and my Windows machine just to make sure. It does start out at 112 MB/s but quickly drops down into the 70 MB/s range and still continues to dip into the 40-50 MB/s range. The transfer speed graph on my Windows machine looks like a lie detector test from a compulsive liar! lol

 

These disks are just acting weird. I had also never seen a controller like mine, the LSI  SAS9201-16, hate a certain model of disk so bad. I've seen a bad backplane rack up UDMA errors but man some of my other 8TB reds racked up like 400 errors in minutes. Like this issue, the writes were fine. All the errors came on reads, and only reads. Again, those controllers are playing perfectly well with all my 2TB drives regardless of make/model.