Hello,

 

I'm encountering a peculiar issue with my secondary unRAID server, which I'm utilizing for backup purposes. Most of the disks in use are repurposed drives, including 2 SMRs of 2TB capacity and a few CMRs (I think), around 500 GB each, originating from external hard drives. Despite these disks having satisfactory SMART reporting, I've noticed an anomaly during the parity sync process.

 

Typically, the disk speed for all drives should hover around 110 MB/s. However, during the parity sync, I've observed an irregular pattern: initially, the speed surges to 100 MB/s and maintains this rate for approximately 10 minutes. Subsequently, it drops to approximately 60 MB/s, and after a couple more minutes, it diminishes even further.

 

Interestingly, if I pause the parity sync for a brief period, say 5 minutes, and then resume it, the speed returns to the expected level.

 

What steps should I take to investigate this issue further?

 

Thank you!

backup-diagnostics-20240326-1607.zip

Those small laptop HDDs probably don't perform well. And your parity disk is SMR which might be the reason a pause helps it out.

1 hour ago, StancuFlorin said:

surges to 100 MB/s and maintains this rate for approximately 10 minutes. Subsequently, it drops to approximately 60 MB/s, and after a couple more minutes, it diminishes even further.

This is typical with some SMR disks.

Ugh. I really didn't want to invest in additional disks for my backup server

 

From what I understood, it is recommended that at least the parity disks should be CMR, right? 

Edited March 26, 20242 yr by StancuFlorin

2 minutes ago, StancuFlorin said:

From what I understood, it is recommended that at least the parity disks should be CMR, right? 

Yes.   SMR as parity disks is likely to sometimes lead to significant performance bottlenecks when copy large amounts of data.

I bought a 2TB Seagate CMR disk to use it as parity disk and the avg speed during the parity check was around 100MB/s