Replace 2tb w/10tb Rebuild at 28mb/s?

[jeffreywhunter]

Version 6.11.5 2022-11-20

LSI 9207-8i SAS Controller

15 drives (balance of SATA ports off motherboard)

 

Replaced a 2 TB functioning (but error indicated) drive with 10 TB drive (Seagate ST10000DM0004 7200RPM 6gb/s) running on the LSI.  Rebuild started running at 28-30mb/s, now running about 50mb/s.  Seems slow.  Just ran a previous replaced drive (2 TB w/ 10TB HGST 7200) and rebuild took about 24 hours with speeds in the 90-120mb/s+ range.  

 

Does that seem slow?

[jeffreywhunter]

Update.  8 Hours later the rebuild is up to 87mb/s, so seems better.  Could the slow build time indicate a problem with the drive?  Based on the latest discussions around preclear, I didn't do it on these two drive replacements.  Should I have?

[ConnerVT]

It is usually a crap shoot trying to diagnose why without a diagnostic file or much info to go on.  Assuming there are no other issues (except for the errors mentioned on the drive being replaced, which shouldn't have any affect), my first guess is that there was some read/write activity happening in the array during the rebuild.  That's assuming the ~30MB/s was happening during the rebuild stage.

 

Speeds during parity check/repair and drive rebuild can be funny when there are different sized drives in an array.  I'll use my array as an example, which has both 8TB and 16TB HGST drives.  Drives access faster on the first tracks, slower on the last tracks.  My read access is basically 250MB/s to start, 150MB/s at the end.  Obviously when you write, it is slower (and slower still when calculating and writing (parity or data).

 

It takes a few moments for the reads of multiple disks to sync up, then will start off at the fastest speed (250MB/s).  As I have 8TB and 16TB, the speed will track that of the smallest drive (8TB), so for the first 50% of the process, speeds will track down to 150MB/s.  After it is done needing to access the 8TB drives, the speed will jump back up to 200MB/S, ramping back down to 150MB/s at the end.  (Remember this is parity check speeds, read only.  Obviously much slower for read/write parity or data rebuild).

 

If there is any sort of array activity happening other than the rebuild operation, the synchronization of the reads gets messed up, so the drives thrash around a bit, really slowing down the drive rebuild.

 

 

[jeffreywhunter]

"Slow/Fast Drives" - That's probably what's happening.  I'm in the process of replacing slow 5900 RPM drives with 7200 more modern drives.  I had turned the mover off during the rebuild so there would not be an issue with writing while rebuilding.  Dockers were all turned off as well...  Its now running 185mb/s, so not sure why so slow for the first 15min, but appears to be working fine now.  Thanks!