I wouldn't recommend doing this, as it appears that you'd almost certainly run into a situation where more than one array is being used at the same time (simultaneous access), and that will slow you down (heads moving like mad).
Best to keep scratch on a separate disks (single disk or RAID) than your working data as it prevents this.
Worth mentioning, as I expect you'd be disappointed when you run into the simultaneous access issue (performance can drop to less than a single disk).
Ok thanks for the heads up
Yup agree completely. In my case, the pair of disks that host the 2 RAID stripes have no other data that is involved in the operations. One RAID is my CS5/NX2 scratch, the other is my sample library when doing music. Neither my photo library nor my MIDI/audio tracks are held on the remaining partitions on those 2 drives, thus avoiding contention.
You would be better off to use a single 3TB drive for your data and a separate small SSD for scratch. BTW, not sure how much RAM you have nor how large your typical PS documents are, but if you are using CS5 you are much better served buying RAM and staying off the scratch disk completely.
I typically work with 12-16 MP images with < 10-15 layers, and never hit the scratch disk at all with 12 GB RAM. I only bothered because NX2 is still 32 bit and can only address 4GB RAM, so it uses the disk constantly.
On the other hand if you are using 35-50 MP medium-format images with dozens of layers, you might care about the scratch disk.
NX2 is Nikon CaptureNX2 - Nikon's RAW editing software for Nikon DSLR's
Thank you again for your advice.
My set up includes:
Mac Pro 3,1 (2008, 2.8 x 8 core)
16 GB RAM (4 x 4GB)
1x ATI 3870
1x ATI 4870
3x 30" Cinema displays
DRIVES
1x Vertex 250 SSD [Boot and Apps, & current working files]
1x WD 320 HDD [Came standard with Mac Pro, partitioned into 2 volumes: 1 for Vertex Clone back up with CCC and remaining 58GB on volume 2 as an alternate boot drive specifically for starting up on to clone the Vertex onto the WD partition 1]
A bunch of externals for back ups/storage/data movement - 3x 1TB WD's, 1x 500GB WD, 1x G-Tech Mini 500GB
2x 3TB Hitachi Deskstar's internals 7200RPM HDD's [ just arrived, waiting allocation ]
I use Photoshop (CS5, CS3), Indesign, Lightroom, Illustrator, planning on using 3D apps, some video as well. I work with similar files, 35MB+ files usually singly. Other times multiple in layers or panoramic.
I have 16GB RAM installed which is probably adequate for just CS5 but I usually typically have multiple apps open on any project, usually about 6+: eg. CS5, LR, Indesign, Word, Illustrator, Acrobat, Safari, Mail, Suitcase, iTunes, Calendar, Textedit, Preview.. so the RAM gets used up fast esp on big CS5 and Indesign documents. I have actually paged out a few times maxing out the 16GB.
As for using an SSD as scratch, I just have the one SSD - the Vertex 250GB which is a couple of years old now. Its formatted at 238GB, 125GB is used with 113 available, so just under half empty. I could use a portion of this available space as a scratch disk, but concerned as its an older SSD whether it would wear it out. Your thoughts/advice on this option?
Your suggestion about more internal RAM is quite a good one which I had not really entertained (as I wanted to avoid investing in old tech, which can't be utilized on newer equipment down the track). I have 4 slots left so could get 2 more 4GB DIMMS but need to check pricing, I'm sure they have come down from 2yrs ago when I bought mine which were pricey.
As to getting a smaller SSD for dedicated scratch, the only problem is I now have 4 drives and all the Mac Pros bays are now used up. Unless I get a tray to use the unused 2nd optical bay eg MaxConnect or Pro Caddy, but want to avoid this if possible as I don't think I have any spare power outputs left as I used one of the spare ones from the optical bay to power the ATI 4870. Which means there may not be any power outputs left for additional drives.
So it sounds like the overall advice is just to use the two 3TB Hitachi's as data storage and back ups?
