Photoshop on a Mac - do I need a scratch disc?

[Terry Zorich]

My educated guess? The internal hard drive would be faster than an external hard drive, whether connected by Firewire or not.

Your BEST bet for a scratch disk would be to use a second internal drive. You can't do that on the iMac, so you're now looking at the next best option, which is probably to use the internal hard drive that you do have; I believe that option would out-perform an external drive, regardless of the interface.

[BobSmith]

Originally Posted by Robert Wilde

Possible you were talking about different firewire speeds? I have Firewire 800,

I was thinking Firewire 800 when I made that post. I know you can do that with your 24" iMac but not my 20". I see little if any speed increase over using the internal drive on my 20" via Firewire 400. The speed increase, if any, comes from having one drive do one thing rather than doing multiple chores, reading/writing multiple sectors on the drive at once. My setup certainly doesn't seem slower than using the internal drive... probably close to the same.

Regarding cases... yes... buy the empty Wiebetech (or other good cases) and populate them with whatever drives you can find at a good cost/performance rate. I use several of the Wiebetech cases where the drive sits in interchangeable trays. Not inexpensive but they work very well, well made, and are extremely convenient to use. I have some of their RAID cases on my server. One of the self contained RAID enclosures connected by Firewire 800 to a 24" iMac ought to give a bit of a performance boost... but now we're back to more noisy fan cooled, multi drive units... and probably not that much of a boost.

Bob Smith

[Jerry Skrocki]

Originally Posted by Robert Wilde

An USB drive is definitely slow.

Regarding the firewire drive, we have opposing statements here. Bob Smith mentioned, using a firewire disc would be faster than using the internal hard drive, and you said it was the other way round.

Maybe we could clear that up?

Possible you were talking about different firewire speeds? I have Firewire 800, which is much faster than 400, and use a g-tech Q Drive external hard drive (hitachi drive inside, and here, too, you pay premium for the reliable enclosure).

The iMac uses a SATA drive internally. SATA drives have a maximum bandwidth of 3.0 Gig/sec with a transfer speed of 300MB/sec. When you connect an external drive these speeds are reduced because of the bottleneck of the interface. In the case of Firewire 800, the maximum bandwidth is 786MB/sec with a transfer speed of 98MB/sec.

[Robert Wilde]

Originally Posted by Jerry Skrocki

The iMac uses a SATA drive internally. SATA drives have a maximum bandwidth of 3.0 Gig/sec with a transfer speed of 300MB/sec. When you connect an external drive these speeds are reduced because of the bottleneck of the interface. In the case of Firewire 800, the maximum bandwidth is 786MB/sec with a transfer speed of 98MB/sec.

Thanks, Jerry. So the easiest and most silent solution is also the fastest solution: my iMac hard disk.

Would you recommend partitioning the hard disk and using a small partition as a scratch disk? Or do you just let Photoshop (CS3) do its spiel?

[Terry Zorich]

Originally Posted by Robert Wilde

Would you recommend partitioning the hard disk and using a small partition as a scratch disk? Or do you just let Photoshop (CS3) do its spiel?

To my knowledge, you need a separate physical disk to see any performance benefit. Using a separate partition on the same physical disk might actually hurt performance.

[Robert Wilde]

I'm getting Martin Evening's Photoshop book hopefully sooner than later. Curious what he's going to propose in regard to a scratch disk.