Fastest partition for scratch disk?

Hi John Nez;

Have you considered SSD?


___________________

Allan

Scratch volumes don't need to worry about saved, and most people use to use half a dozen drives in RAID0.

The most important today is to have excess memory, virtual volume cache, so you don't hit scratch.

Some people use SSD, others warn about high I/O of useing SSD for scratch.

Or there are your fast 10K WD VelociRaptors and setup those in RAID0.

As long as you have good backups, RAID0 is fine.

Save while you work to another location.

And people do use RAID0 for system and apps, whether pair of SSDs or other types of drives.

In 10 yrs I can't recall having much trouble if any, and I use RAID to boot from, for data and media files.

IF you never did RAID then experiment in ways that work and are safe. Or don't use it at all.

http://macperformanceguide.com/OptimizingPhotoshopCS5-Intro.html

So I'm going to use a scratch disk with Photoshop.

That is laudable, but you should understand that Scratch is a way to edit files that are too large for the RAM you have in your Mac. You can still edit those files, but s-l-o-w-l-y.

which is the fastest partition?
Is the fastest partition the one at the top of the Disk Utilities window?

Of all the partitions, the one at the top will be slightly faster. But anything that moves the heads of that drive away from the scratch area, such as reading another file on the same drive, will slow the process enormously -- far more than the difference between first and last partitions.

When a RAID file fails, is the file entirely ruined on every RAID drive?

I assume you are talking about RAID striping. RAID striping slices your files into chunks or stripes, and the stripes are written alternatively to two or more drives.

The speedup comes from the second (and third, if present) drive seeking the next stripe while the first drive is still transferring the previous stripe.

If a drive fails, not only is your file lost, the entire logical Volume stored on the two-drive set is lost, with very little hope of recovery of ANYTHING. Half the data from every file and large portions of the directory is simply not accessible.

This is somewhat more precarious than a single drive failure because the expected failure rates of the drives are added, making failure of the striped Volume more likely. Some scoff at this additional risk, reminding us that "any drive can fail at any time."

The bottom line for me is that you MUST be religious about having a backup copy when using striping.

Scratch means never having to worry about failure, it is after all SCRATCH and is meant to be erased all the time.

But not if you plan to use the drive for other uses.