use old raptor drives in new build or get rid of 'em?

The Raptors will almost surely perform better than the Caviar. Here is a direct comparison showing that even a single Raptor WD750GD outperforms the Caviar: http://techreport.com/articles.x/8497/6

Hope this helps!

They are still best-in-class as far as I can tell.

Yep, keep 'em in RAID0, unless youdecide to drop loads of cash on the new VelociRaptors.   $300/per @300GB

Use them for the OS, most OS don't read vast amount or sequential data and do lots of random access so probably a perfect fit for Raptors. I reused my old 36GB Raptor for my new build's OS drive and I am very happy with that. I put games and bulkier applications on a Seagate 7200.11.

Well, that article was from June 30, 2005 showing a 250GB drive. That 640GB, 2 platter drive, I believe was released recently. I would still keep the two raptors in raid-0 and use the 640 as a storage drive.

Sweet baby jesus, I feel like I've been researching drive comparisons and raid 0 cluster/stripe sizes forever. The first thing I'll say is that I'm not even sure that the 740GD drives in RAID 0 for an OS drive are even preferable. I did see a comparison between the 640 GB Caviar and the 2nd generation 74GB raptor with the 16MB cache in RAID0, and the Raptor RAID was barely beating the 640gb caviar, and that was the 16MB raptor. Also, came across some information saying something about striping not being equally lined up between the 2 drives when used as a OS drive.

But that aside, There are soooooo many different opinions about what size to make cluster/striping size. It kind of seems like you would want the 4k cluster/16k striping for an OS RAID0 setup, and maybe a 16k cluster for storage drive(though not sure if 16k cluster causes defrag problems), but you also find people suggesting 64k striping or 128 k striping

So, to sum up the questions I still have:
What is this deal about an OS raid drive not having striping equally "lined up" on both drives somehow? I wish I could remember the term they used for it. Something about a boot partition being created on one drive that throws it off and needing to use really big striping to fix it, otherwise losing 20% or so performance.

Also, I know that ideal stripe size can sometimes depend on the controller(I have a gigabyte GA-EP35-DS3R so the southbridge SATA and the 2 gigabyte SATA), but for an OS RAID0 config is 4k cluster and 16k striping the way to go?

The ONLY reason I have done away with my 74 GB Raptors in RAID 0 on my rig is that I replaced them with the new 300 GB VelociRaptor. It all depends on what your needs are. You could keep them and add something like the WD6400AAKS as a data drive and probably survive another few years...or if you want speed...the new VelociRaptor is a bit faster as a sngle drive than my old 74 GB Raptors in RAID...by about 20%. You are in a win win scenario...

A RAID controller adds latency to the drive so it might kill part of the Raptor's edge. Raptor's strength is random access time, not bulk transfer, by putting them in RAID you might negate it's strength to compensate for its not-that-annoying shortcoming, ending-up with an overpriced storage geared toward sequential read/write performance.

Maybe you could just use them in non-RAID mode and get a second disk better at bulk storage.

Perhaps...but not significantly...see here:

http://www.extremetech.com/article2/0,2845,2288834,00.a...

Overall...you lose about 4% on the access time...going from 7.0 to 7.3 ms. RAID still has benefits...

Bob