6.12.3 - Slow write speeds after 1 - 2 hours

[venserss]

TLDR: Write speeds are fast to start off (165 - 150) then will slow way down after about an hour or so. Not through network, all through the server. Moving data from one drive (using 'unassigned devices') to the array using Krusader. Removed parity from the array to see if that was the issue. It was not. Problem still persisted. Turned on Reconstructive Write and though the speeds increased, still ran into the same issue. If i pause the data xfer through Krusader for a bit, the speeds will come back, again, only for a little bit.

 

I've been hitting my head against a wall, and I cannot seem to find an answer to the issue that I'm running into and I have a feeling it has something to do with a setting I'm missing or a config that isn't right.

 

Current Setup

MPG Z390 GAMING PRO CARBON AC (MS-7B17) , Version 1.0

i5-8500

64gb DDR4 (non ECC)

4 Seagate 6TB Archive - Disk speed test all good XFS

1 Seagate 8TB Compute - Disk speed test all good XFS

1 WD 500GB Blue SSD XFS

 

I thought for a moment that it might be the disks themselves so i installed the 8TB in my Dell RV320 and transferred 7TB of information to it with no issues. The next thought would be "well then it's the 6TB drives" but i don't think it is. I originally started with 3 8TB and a parity 8tb drive (all Seagate Compute) and ran into the same issue. I would have good speeds for a bit. It would fall to 50mb and then fall more over time. I also tried switching out the cache disk and making it an 8TB drive so that ALL of the data could go to cache and then dump as needed. Still the same issue. Start fast -> 1-2 hours -> 1-2mb speeds.

 

I have played with mover settings, array settings, and googled a lot but can't find anything. 

 

I'm new to a alot of this, not to savvy on getting diagnostics but would love to if pointed in the right direction. I'm liking the software thus far and this has been my only hangup, but it's a big one.

 

tower-diagnostics-20230815-1658.zip

Edited August 15, 2023 by venserss
Diagnostic attach

[trurl]

2 minutes ago, venserss said:

not to savvy on getting diagnostics

Click that link in your post (or mine) to find out how to get Diagnostics 

[venserss]

Attached Diag to OG post, thank you for helping / pointing it out. 

[JorgeB]

All you disks are SMR, SMR disks tend to downgrade write performance after some GBs written, some models are worse than others.

[venserss]

3 hours ago, JorgeB said:

All you disks are SMR, SMR disks tend to downgrade write performance after some GBs written, some models are worse than others.

Ah, thats a place i can start to look. Though no issues pop up for any of the disks when writing within Windows Server. Speeds for both the 6TB and the 8TB drives (Archive and Compute) stay at a constant 100+ for the entire transfer (4+ TB)

[venserss]

Hopefully I can save somebody the headache of dealing with this monster of an issue. There is a lot to cover when it comes to the ins and outs of SMR but overall, there are these reverberated words.

- SMR will write slower over the duration of your transfer. (we're talking 1TB+) This is because of how the disks stores data and a kind of "lock up" that the disk will run into when its cache (Not the unraid cache, the DISK ITSELFs cache) fills up.

- 1 - 2 Mb/s is normal when it gets into this locked state.

 

Honestly google "SMR disk write speeds" and you will get slapped in the face with a lot of peole running into the same issue. I don't think that I ran into the issue on Windows because of some kind of SMR handling Windows has idk..