Adaptec RAID 7805 create mirror?

As dlethe noted, if this is for a boot disk, you first need to confirm you can even use it.

But if it's just for storage, then there's no problem.

To answer you actual question, creating a RAID-4 mirror on a set of 4TB drives should take in the neighborhood of 10 hours if they're 7200rpm drives; about 12-14 on lower RPM "green" units, depending on the specific model.    The Seagate DM series drives should be in the 12 hour range.    These times can be notably longer if the RAID software does a full verification run after the array is created (nearly double) ... but I don't believe that's the case with the Adaptec controller.

another alternative ... the 7805 does have background init, so you could technically just build & configure the RAID1, wait a minute, then start installing the O/S.  

It will do a full RAID1 init in background while you use the system in foreground.  It could very well end up taking > 24 hours before the RAID is fully initialized, but you could start using the system immediately.

Down side, I/O will be significantly slower, and you have no protection against data loss  until the entire disk has been initialized.  Still, you could use the system immediately after kicking off the init.

With two 2TB drives it took in my case 16 Hours.

The actual time depends on a variety of factors -- primarily the controller; the drive's rpm;  and the areal density (clearly new 1TB/platter drives are much faster than the older 500MB/platter units).

Hi,

Thanks for the responses - if I was creating a raid 5 set instead would it add a third more time - 3 drives instead of 2 that is.

Thanks

Ward