Welcome to the MacNN Forums.

pstinnett · Dec 29, 2006, 12:53 PM

does anyone know about enclosures that hold 2 hard drives (like this one)

I'm thinking about getting it and 2x300gb hard drives. in OS X would they appear on the desktop as 2 seperate drives or just one drive? I'm hoping they would appear as 2 drives, but I'd like to know before buying the case. Also, is the speed affected by only having one USB2.0 connector?

Any pros/cons to having a 2 HD external case?

indigoimac · Dec 29, 2006, 03:44 PM

Well it kinda depends on the enclosure, the one you have linked to I have no idea, but the first one below will have them show up as 2 drives and the 2nd will make the drives appear as one 600gig volume using a RAID 0 Setup.

OWC Mercury Elite-AL 800 Pro RAID Ready Fi... (MEFW924AL2R) at OWC
OWC Mercury Elite-AL 800 Pro RAID-0 Stripe... (MEFW924AL2) at OWC

The first link is the only enclosure that I have found (and will be ordering shortly) that has firewire and will have the drives show up as separate volumes.

Also in regards to speed it will only really suffer when u are reading/writing to both drives, and USB is proably not the best choice when you are looking for transfer speeds, especially w/ multiple hardrives, if you can afford is the two I linked to above are better choices.

I also just noticed that you seem to want an ATA enclosure, rather than SATA, in that case the enclosures that I posted will not work unless you choose SATA drives.

pstinnett · Dec 29, 2006, 03:58 PM

The only problem with those enclosures are the price

I guess I don't need so much speed. I keep all my music on my external hard drive (90 some gigs) and I have a lot of videos/things that I've downloaded that I would like to archive on a harddrive rather than dvds. I'd also like to keep a backup of my powerbook's HD that updates once a week.

I was thinking of having one HD as music/video and then maybe a smaller one for backing up the powerbook. What do you recommend I do? I suppose i don't really need the dual HD enclosure.

mduell · Dec 29, 2006, 04:03 PM

That enclosure will present the drives to the OS as two separate drives. The product page specifically notes that the enclosure does not support RAID.

The enclosure is effectively two ATA<->USB bridges with a USB hub integrated inside. When accessing both drives at the same time, the performance would be lower than accessing two USB enclosures on independent busses (if your Mac is so-equipped).

pstinnett · Dec 29, 2006, 04:05 PM

that summed it up perfectly.

how much of a performance loss do you think there would be? anything drastic?

also: will the enclosure still work if I only buy one drive at a time? for instance, I might just buy 1 drive for now, and later upgrade to 2 drives. can it work as a single or dual enclosure?

indigoimac · Dec 29, 2006, 04:21 PM

Originally Posted by pstinnett

that summed it up perfectly.

how much of a performance loss do you think there would be? anything drastic?

also: will the enclosure still work if I only buy one drive at a time? for instance, I might just buy 1 drive for now, and later upgrade to 2 drives. can it work as a single or dual enclosure?

I really don't know about performance, I myself am sort of interested in this.

I believe that the enclosure will work w/ only one drive or mismathed drives, and on a sidenote if you really don't need a two drive enclosure for that same price(or significantly less) you can get an ATA enclosure w/ Firewire which will perform better than USB2, but for what you are doing USB2 will probably be fine.

mduell · Dec 29, 2006, 06:02 PM

It looks like the enclosure will be fine with one drive or mismatched drives.

The performance loss is half; you're putting two drives on one pipe instead of one. So you can access one drive at ~30MBps, or both simultaneously at ~15MBps. For your previously mentioned uses the performance should be fine.

pstinnett · Dec 29, 2006, 07:07 PM

great. and if i need to copy anything from the drives i can always just stop accessing the music portion for a bit. thanks for you alls help.

mduell · Dec 29, 2006, 10:09 PM

Originally Posted by pstinnett

great. and if i need to copy anything from the drives i can always just stop accessing the music portion for a bit. thanks for you alls help.

If you're on an OS that supports I/O prioritization, then you can keep playing your music while allowing the transfer between drives to continue with whatever bandwidth is left over. I know Vista supports this, but I don't think OSX is there yet (even in Leopard).