Using multiple harddrives at same time?

There are enclosures that can handle from various numbers of drives. USB 3.0 will be fast enough to handle 3 HDs on the same USB port.

You also have the option of adding the drives to a Thunderbolt enclosure, but that would be more expensive. And there is the option of adding more USB 3.0 ports with a thunderbolt dock.

 

I agree with Bear, there are plenty of enclosures you can buy. Just doing a cursory search on Newegg, a USB 3.0 4-bay enclosure can be had for $100. I did note that several of the enclosures needed a firmware update to keep them from disconnecting in OSX, so just be aware of that.

 

If you have 4 regular HDs, USB 3.0 won't be a bottleneck. Thunderbolt is faster, but of course your speed would be limited by the devices you're connecting.

 

Agreed. The throughput of USB 3.0 is 5Bps, Thunderbolt is 10Gbps, SATA 3 hard drives is 600MBps. If you hit all the theoretical limits, you'd max out even Thunderbolt with only 2 drives. Realistically though, I seriously doubt you're going to be throwing the full, sustained data rate at those drives. You address each of those drives separately on the bus, not combined.
If you needed that much throughput you'd know it & wouldn't even be asking the question here. I'd have no problem using 3-4 drives in a JBOD configuration like that.

 

That's the SATA 3 limit, however HDs only use a fraction of that. SSDs come closer to maxing out SATA 3.

 

Exactly. Like I said, "If you hit all the theoretical limits". The fastest mainstream SSD (Samsung 840 Pro) only reads at 540MB/s and writes slower than that. At full utilization, you could still have 4 of the 840's on one Thunderbolt channel and still not max it out. USB 3.0 is plenty enough for platter disks. The Western Digital Black drives only max out at 154MB/s sustained. So that 5Gb/s USB 3.0 channel could realistically support 4 of the black drives simultaneously at full throughput, which will never happen (and no, that's not taking into account USB 3.0 is full duplex as well).

 

There was just an SSD released the other day that the person on Mac Performance Guide hooked up to a trashcan, um, mac "pro" via thunderbolt with 4 SSDs. So yes, multidrive enclosures are out there and they are fast.

 

"Ideally, I would like one enclosure that I can place 3-4 drives in it, and it would have a single power supply and one USB 3.0 or Thunderbolt cable connecting to the iMac, and ALL 3 drives would be mounted simultaneously."

Before you go this route, ask yourself a question:
Do you want to keep "all your eggs" in one "basket"?

It might be wiser to keep drives as "individual units", if they are not otherwise "bound together" (such as in a RAID array).

Makes drive/enclosure failures MUCH easier to fix….

 

I have a Mac mini with 4 drives mounted over Thunderbolt all the time and an additional 3 drives mounted over Firewire. You will have no problem running a couple externals from an iMac. For performance sake, I strongly recommend Thunderbolt over USB.