Drive configurations

[macstatic]

Which hard drive/SSD configurations should I consider for a Mac Pro (2.66GHz Quad 2009 Mac Pro) optimized for photography (currently Photoshop CS4 and Lightroom 3). The Mac Performance Guide suggests:
- OSX/apps: 1x fast SSD drive
- User area/files: 2x high performance hard drives in RAID 0 (striped)
- Time machine backup: 2x high performance hard drives in RAID 0 (striped)

But what should be used as a scratch disk? A separate partition of the SSD drive? I suppose the backup drive would also suffice.
I'm also concerned about using RAID 0 as that would mean a total failure if one drive fails, but then again having Time Machine do hourly backups (plus manual ones after large jobs in between) should be pretty safe. I guess I could choose RAID 1 (mirroring) for the backup drives as speed isn't critical here and that would mean two independant backups should one drive die, but then this drive would be no good for a scratch drive as well because of lower performance. What do you suggest I do?

 

[hfg]

I wouldn't use a RAID-0 for backup ... ever ... !

I would also put my Time Machine backup external to the Mac Pro so something like a power supply failure wouldn't take everything with it. You don't need speed for backup (i.e. RAID-0), but redundancy like RAID-1 or RAID-5 would be nice just to protect from a drive failure (actually 2 separate drive enclosures and locations would be best).

Since the internal ports on the Mac Pro are all SATA-II, I run mine with a RAID-0 pair of SSDs for boot/os x/ apps and a RAID-0 pair of 1TB hard disk for data libraries.

You could possibly put a scratch disk on a Velocity Solo X2 PCIe card mounted SSD for speed.

My backup is a external eSATA RAID-5 box in addition to a basement Synology NAS system on my network. Time Machine alternates between the systems for each hourly incremental backup.

 

[macstatic]

Hadn't though of power supply failures. An UPS would probably be a good investment as well, "cleaning up" power spikes etc. which I suspect could damage a power supply and computer memory in the first place.

For external storage I already have a Proavio S4 4-bay removable drive enclosure (Firewire 800). I should be able to use that for external backups (I currently use it for data storage (and backup/archive backup sets of those drives) with my Powerbook G4. Chronosync is used to perform the backups.
I suppose with a dual drive mirrored setup (RAID 1) in the Mac Pro and external backups to the S4 rack I should be OK. NAS, RAID-5 etc. will have to wait for now -investing in a Mac Pro with all the upgrades/expansions will put enough strain on the wallet for a while

SSDs: I've heard that lots of disk-write operations will quickly kill an SSD, but perhaps this is a thing of the past. OWC seems to claim that their SSDs are superior to others in that respect. But in any case, is this something to be concerned about when thinking about assigning an SSD to a scratch disk?
Also, I read differing reports about performance improvement or not with SSDs on a Mac Pro. It makes sense that using an SSD for a boot/app drive doesn't actually increase performance (i.e. higher speeds when working within an application except if the application constantly accesses new plugins or whatever) but allows for faster startup times. I assume a fast scratch disk would be more important for Photoshop use (other apps that use a scratch disk as well?).

What puzzles me is what kind of SSD (brand/model) to get and if getting one with SATA-III (along with a SATA-III PCIe interface as the Apricorn Velocity Solo x2 you suggested for $99 without any SSDs) will make a big enough difference in speed for most users to justify the added cost in comparison to using the Mac Pro internal SATA-II interface or not? The Mac Performance Guide (MPG) suggests RAID-0 striping with two 6G SSDs on a SATA-III bus, but I understand his site caters for extreme performance-demanding users...

I've also read about the more expensive Sonnet Tempo SSD Pro which seems to be similar to the Velocity Solo x2 but more expensive ($300 without any SSDs) but attaches both SSDs to the card itself (unlike the Solo x2 which only takes one SSD and attaches to a second SSD via SATA and power cables -I assume that SSD typically goes in the free optical drive bay). The Sonnet is reported not to be bootable though (the Solo x2 is).
Finally I've read about the OWC Mercury Accelsior ($320 for the 120GB version) which gets high praises in the MPG. From what I understand this PCIe card actually consists of 2 SSD drives set up in RAID-0 (striped) mode for maximum performance. It's bootable and only $20 more than the Sonnet, but with SSD! I guess you need to partition it into two drives if you want to assign two separate SSD drives as with the Sonnet, but I'm guessing performance would suffer in the same way as partitioning a physical HDD.
If I want a fast OSX boot/fast starting of apps as well as a fast scratch disk within a limited budget, what would you suggest among all these setups?