How long does it takes to rebuild an array?

[jon96789]

My TS-853A had seven 4TB drives in a RAID-6 config. I decided to fill the last bay with another 4TB drive (all WD Red Plus) to expand the array to 24TB (21.5TB net space). It took 48 hours to "migrate" data and now it is saying it will takes another 36 hours to rebuild the array. Is this normal? I know I have a lot of data, about 13TB.

On a side note, right in the middle of everything, the drive in bay-2 failed. Thank goodness for RAID-6. If it was RAID-5, would I have lost my data? I just bought a TS-673A to backup the older NAS.

[holger_kuehn]

I decided to fill the last bay with another 4TB drive (all WD Red Plus) to expand the array to 24TB (21.5TB net space). It took 48 hours to "migrate" data and now it is saying it will takes another 36 hours to rebuild the array. Is this normal? I know I have a lot of data, about 13TB.

The used quota is not relevant for this. It's the internal storage-structure of those 24TB. I had a few 8-bay-QNAPs, if I remember correctly it took about 24h each.

On a side note, right in the middle of everything, the drive in bay-2 failed.

Maybe drive 2 had some trouble and slowed the process down.

If it was RAID-5, would I have lost my data?

Did you migrate from RAID-5 to RAID-6 by adding the new drive? Your statement did not sound like it, as you get more space.
If you already had RAID-6 you should be fine even when loosing two drives. So I don't think, you'd have lost data.

But I'm always using RAID-6, especially with those larger drives (10+ TB). Gives me much easier nights, not regarding backup but availability.