SSD scratch disk life span?

Would it be detrimental to the life span of a SSD if it were used for a scratch disk? I'm building a workstation computer used fro Adobe + CAD + 3d Rendering Softwares. I want to provide a general RAID 0 2x2tb hdd for main data, 1 ssd for os+programs, 1 ssd for scratch disk. The plan is to provide a smaller 40 - 64gb ssd for the scratch disk. I got several concerns with this choice:

1. Will it shorten the lifespan of modern SSD's with TRIM on Windows 7.

2. Would it be smart to focus on a SSD that is equal in read/write? (I've seen the read is usually much less than the write speeds... this is good for OS + Program setups where reading is the most important but isn't scratch disks heavy read/write operations?)

3. Would my system's performance benefit more if I put the HDD's or SSD's to a SATA III connection (which one would be smarter to put to the 6gb/s connection vs. the 3gb/s connection... I have two 6gb/s spots available = 1x Raid0 HDDs or the two SSDs).

4. Any recommendations on either HDD or SSD that would be preferable for a scratch disk is much appreciated.

Of course it will shorten the lifespan. It's the same with any disk, SSD or spinner. The more you use it the shorter its lifespan. I'm not sure the 6Gb/s connection will actually provide any benefit. I vaguely remember reading that most current SATA III implementations are pretty poor, but I'm not absolutely sure. Without knowing what motherboard you're using it's impossible to make that call about your system anyway.

SSDs have an absolute write limit beyond which they start failing to accept new data (unlike hard drives, whose mechanical parts may or may not wear out faster with heavier use, see the Google study on disk failure rates). So the more you write to an SSD, the faster it will wear out.

Using an SSD as a scratch disk will tend to subject it to more writes, since files that are written to it are used only briefly and then deleted (unlike an OS disk, whose files are written to the drive and then are re-read many, many times).

That having been said, whether it's a big issue or not depends on how much writing you do. Intel claims their X-25M G2 drives will last "at least" 5 years if you write 20GB/day to them. The Intel SSD Toolbox shows how many GB have been written to the SSD, and my Windows 7 system is averaging about 5GB/day. Even if that was doubled as a result of scratch file writes then you'd still be looking at about 10 years of life, by which time the drive would be pretty much obsolete anyway.

You also have to consider whether the added performance will boost your productivity enough to offset the cost of the SSD and the potential cost of a replacement, which will of course be cheaper, larger and probably last longer than the first.

I know I'm in the minority on this issue, but
I'd highly recommend 2 of these WD5003ABYX in RAID 0:

http://www.newegg.com/Product/Prod [...] 6822136697

ATTO consistently reports 150 MB/second at the outermost tracks
and this HDD is truly Plug-and-Play!

However, WD does NOT report this measurement in their specs:
they prefer to report a "sustained" rate which is usually quite lower:

http://www.wdc.com/wdproducts/libr [...] 701338.pdf

So, "short-stroke" a smaller primary partition
e.g. 50 GB total will use only the first ~25 GB on each HDD:

http://www.supremelaw.org/systems/ [...] aphs.2.png

Perpendicular magnetic recording not only records bits closer together;
it also permits adjacent tracks to be much closer to each other as well.

MRFS

Do scratch disks really require much space. I was intending t to buy a 40 - 80gb sized drive to take care of the space i needed for 'scratch'. I'm not sure I'm aware of what the scratch disk sizes need. I edit some large .tiff + .raw files but i didn't think i was going to need more than the size listed above. From the sounds of it I need about 500gb for 'scratch' space. This is super large from what I thought i needed. can anyone tell me why so much space is needed or at least being recommended to me. I'm not doing much AVI or HD work. Just static stuff.

It totally depends on what you're doing. Movie editing tends to require a LOT of scratch space. Editing photos, RAW or otherwise, shouldn't require a whole lot if you edit one at a time. But if you try to stitch together a large panorama from dozens of shots then it'll be a different story.

The best thing to do is to configure the scratch files onto an HDD and watch what happens to its free space as you do what you consider to be the heaviest editing job you expect to handle. The drop in free space should give you a pretty good idea of how much scratch space is being used (assuming you're not doing something else like downloading files from the Internet at the same time).