DSM 7.1 'Replace' function takes 6+ days!?

[Ltek]

My 1019+ has 4x6TB SHR array (one empty bay). I want to swap all the 6TB for 12TB, one at a time of course - using the empty bay. Thought I would use the new 'Replace' functionality and it would be fast and easy. Well... its been 2.5hrs and it says only 1.75% complete and will take over 6 more days!? The drives are 80% full so that means it only has to copy over 4TB of data. Should take a few hours at most, correct?

Anyone know what is happening here? ... rebuilding from a failed drive takes less time I'm pretty sure.

TIA!

 

[fredbert]

It's not just copying over one drive's data, it's re-syncing all the parity data across the array. There is a speed setting in Global Settings that may help a little.

 

[Quantillion]

I had less to replace: 2x 7TB drives, 90% full, SHR, one of which was "failing" (so ~6To of data to copy) so I replaced it & it took almost 3 days. (Write at 77MB/s max [for my DS416; let's say 25 MB/s for multiple small files & syncing] offers 6TB written in 2.8 days, so quite normal.)
I then added 2 disks (identical) to fill my 4 bays & that was quite quick.

 

[Lewis]

What drives do you use ? If is SMR (instead CMR) it might be reason for such slowness (last year I was replacing 8TB with 14TB drives and each drive took about 50 hours to complete (with CMR drives) so in total it took me 8-9 days for 4 drives)

 

[Ltek]

UPDATE approx 16 hours after starting the Replace function... DSM shows 60% competed w/ 4 Hours left. Much better!

@fredbert... Wonder excatly how it does the Replace. Curious if it treats both new/old drive as a mirror'd pair inside of the Array replicating all writes to both drives... and coping the rest of the data as it goes. Then, at the end, compare / look for deltas to update just in case anything was missed.

@Quantillion ... thx for the info. with your results, mine looks like it will take around 1 day if DSM is now correct on its estimate. DSM's 6 day estimate it gave for the first few hours is way off - thankfully. I'm replacing a drive with 4TB and very little new data ever written to the array.

@Lewis ... All drives are CMR with fast transfer rates - new ones are Seagate EXOS 12GB x18 (very fast drives), the old ones are Toshiba 7200rpm

 

[fredbert]

@fredbert... Wonder excatly how it does the Replace. Curious if it treats both new/old drive as a mirror'd pair inside of the Array replicating all writes to both drives... and coping the rest of the data as it goes. Then, at the end, compare / look for deltas to update just in case anything was missed.

Good question! I don’t know. I just hope that if I need it then it does the least risk way of switching over.