How best to set up a scratch disk for photoshop?

[Fiercehairdo]

Hi,

I have a new mac pro with 4 int hard drives (the original boot drive and 3 x 1TB int hard drives).

How should I configure the the drives for photoshop scratch disk?

I intend to have the three int hard drives as a single striped RAID for all my data storage. Can I use the data storage RAID as the scratch disk or is it bad practice to have thesame disks that I'm storing files on as the scratch disk?

Should I have a dedicated internal disk as a scratch disk?

Or, will an external HD connected via a eSATA port be adequate for a scratch disk?

Thanks.

 

[snberk103]

Congratulations on your new MP! I found this site(Mac Performance Guide) to be invaluable. Its not actually loading for me at the time, ... I hope its a temporary glitch at their end. Full of advice on how to optimize your Mac Pro, scratch disks, optimize Photoshop, etc. I've started with its suggestions, and have seen some speed gains. More memory arrives next Monday or Tuesday, and I should see more yet.

Cheers

 

[pprior]

Yes it's bad practice to have the same drive for scratch and for data.

It's also bad practice to have all data stored on a 3 drive stripe unless you have a very good backup system in place.

Is there a reason you need the striped array?

The link above is a good one.

external drives are not the best choice for scratch, unless eSATA.

 

[Fiercehairdo]

Yes it's bad practice to have the same drive for scratch and for data.

It's also bad practice to have all data stored on a 3 drive stripe unless you have a very good backup system in place.

Is there a reason you need the striped array?

The link above is a good one.

external drives are not the best choice for scratch, unless eSATA.

I would like the striped array for speed and efficiency purposes. As I understand it, saving, opening and general disk activity will be much faster on a striped array - is that correct?

I intend to have hourly or at least daily back ups of all the work on the RAID array to external hard drives.

I have a Sonnet Tempo E4P SATA card installed so I thought I could have the Ps scratch disk on an external disk or external disk array thereby freeing up all my internal disks (3 1TB disks not including the Boot drive which I will only use for apps) for the data storage array.

Any comments on this plan are most welcome...

 

[ChrisA]

I intend to have the three int hard drives as a single striped RAID for all my data storage. [/QUOTE

First off Photoshop scratch files where a bigger deal back when RAM was measured in megabytes. Today with gigabyte sized RAM scratchfiles are not so important.

So your system is be three time less reliable. You can literally expect the 3X higher chance of a failur that will cause loss of data. I would ONLY recommend a stripped disk array for holding scratch data, that is data you don't mind loosing. A typical use the a three way stripped array is for video editing, to hold the media files. You never need to care because all you work is contained in the EDL files that would be in your home/documents folder and the media would be backed up or could be re-imported from tapes. The stripped array is an ideal place to put your Adobe scratch files too. But not data you care about.

If you are working on a budget it would be best to spend your money on more RAM before you spend it on a three way stripped array. Only buy the array if you have enough funds to both max out the system RAM and buy the array. The RAM is used by Mac OS as a disk cache which is much faster then an array.

A Mirrored array can actually help system reliability and can help with read performance too. reading from a mirror can be as fast as reading from a stripped array but writing can be up to twice as slow.

For photoshop, the disk will not be the performance bottle neck. So no matter what you do it will have little effect that anyone could notice. RAM will help the most

Yes I did read about a backup plan to a RAID but...
1) Is this an INCREMENTAL backup that does NOT over-write old data? Time machine does the right thing but absolutly do not make periodic "clones" of the array or periodic "syncs" of the data. Because when the failure happens (and it will with a stripped aray) then you will over write your good backup with corrupted data.
2) Is there a second off-site array? Theft of equipment and fire are leading causes of data loss. Also remember that EVERYONE who has had a fire, before the fire said "I've never had a problem with fires."