How long should a RAID Reconfiguration take? (Adaptec 6805)

I have an Adaptec 5405Z with 20x2TB 7200 RPM drives on a SAS Backplane. I attempted to do a reconfig on it to go from 8 drives to 20 drives. We use it for Security Video Storage. Since the box was essentially brand new, I figured why not see how long it woudl take with ~2TB of data on the array. After about a week and it only getting to 10%, I gave up. Backed it up, wiped it and started over. I tried the same test with RAID 10 and RAID 5, both seemed to crawl, but would have eventually finished. Though in truth, I am certain my DVR software was slowing down the reconfig by constantly writing to the disk. Did you factor additional load on the drives into the rebuild?

Obviously I have a few more drives than you, but for whatever reason, the reconfig seems to drag on for quite some time. When I tried to get Adaptec to answer the question, they weren't much help as the answer seemed to be "it depends on your configuration and how much data is on the array".

• Normal is relative. It should take some hours to reconfigure online. The exact time should be the size of the disc divided by the throughput of a single drive plus some small overhead. With active usage the small overhead would transform to a bigger overhead. But 24 hours with no progress is too long.
• Yes you can estimate that this is the exact time needed in case of a recovery.
• It should be possible. From within the controller's configuration setup during boot up.

The 0% bit is a bit odd but if the array was completely empty I'd expect the reconfiguration to be done quite quickly, certainly under an hour. That said if there's data on it then this kind of thing can take days, and those disks are big and slow so that won't help either. And that is indicative of how long rebuilds can take, it's why sysadmins don't like to use R5 or R6 when using large, slow disks - rebuilds take ages and expose you to risk while they do so.

If you have no data on the array or you can quickly move it to another drive then consider destroying the array and rebuilding it as you need. Personally I'd have bought 3TB drives and R10's them but that's your call.