I have two older PCs on my LAN posing as 'servers'; one running FreeNAS off a USB stick using three 500GB HDDs in a ZFS RAID-Z pool serving as storage for the LAN and one running Debian Lenny with an 80GB drive used as a general purpose 'tinker' box that I can ssh into, etc. Problem is that the SMART report for one of those 500GB drives in the FreeNAS box is showing some pre-failure attributes, and the whole array is a little small anyways. Rather than simply replace one 500GB drive with another 500GB drive, and have no backup of the file server, I'd like to upgrade all the drives to 2TB ones - but I have no where to store that much data in the mean while. As such, I started looking at getting a 4-bay external drive enclosure with an eSATA card for the Debian box, with the hopes of creating a RAID5 + LVM setup using those drives and backing the data up to that external drive enclosure. After the backup is done, replace the drives in the FreeNAS box and rebuild the array there and mirror the data back. Then, I'd have both the primary storage (on the FreeNAS box) and a backup (which I don't have currently) using the external drive enclosure on the Debian box.
My big question is... most of these external drive boxes seem to claim support for JBOD, RAID 0, 1, 10, 5, etc. - should I presume that is simply fake RAID like many commodity mobos have, and not really usable in Linux? In that case, with all the drives hanging off the one eSATA connection, will Linux (specifically Debian Squeeze, as I plan on upgrading that box here shortly) see all four drives, or just the first one? Will I be able to configure them in a RAID5 array as desired?