Ah OK that's different... your plan below looks about right then.
Well, the typical fast SSD on a SATA III profiles about like this:
And you can clip all of the over 300 MB/s to about 295 to 300MB/s for SATA II. Of course double everything for a 2-Drive RAID.
A 2-drive RAID0 using rotational drives (Seagate Barracuda ST3000DM001-1CH166) looks like this:
And a 4-drive RAID0 using the same 3TB drives ($130ea) looks about like:
Those marks are sequential sustained but like 1 or 2MB files for random I/O looks close to the same as those. Notice that the 4-drive RAID0 is not 4 times the speed as a single drive like 2 drives double a single's speed. It's a diminishing returns thing or something. Given that the Seagates do about 210MB/s actual, it goes something like this:
1 Drive: 210MB/s
2 Drives 390MB/s
3 Drives 540MB/s
4 Drives 640MB/s
And then for some reason you get another 100MB/s for every additional drive you add up to 6 (which is the most I've tried on a Mac). These top speeds are typically maintained across 60 to 70% of the drive's surface but with these Seagates it's more like 85% which is unusual - and I dunno why. So when using rotational drives in a RAID or even as a single drive it's a good idea to short-stroke the drives to like 80% or so - via partitioning. Either that just be mindful not to fill the volume(s) past about 80% - either way.
Hmm, well, there's three themes not two. There's the OS and Apps. Then there's the Application Data (movies, photos, MP3s, miscellaneous files, etc.). And then there's the backup. The first two you got right but the backup should be of everything you don't wanna lose and it should be external not internal. I keep a backup of
everything except downloaded MP3s and DVD Rips. If it's important stuff like work files or family photos then multiple rotated backups preferably with one of the rotated volumes kept off-site (like at the office or a relative's house).
If you don't need that much space for application data then you can cut some costs but I wouldn't eliminate or compromise the third theme.
For example:
- Application Data - Four 2TB Barracuda Drives at $70ea.
- OS X and Apps - Two 250GB Samsung 840 series SSDs at $200ea.
- Backup kit:
- A USB3 Thermaltake dual drive dock at $60
- Two or three 4TB Barracuda drives at $170ea.
- A USB 3.0 Card at like, $20
Is like $1,100 in total if only two 4TB drives. If you went with four 1TB drives for the application data then you could get under the $1k you mentioned. You might only need 3TB drives in the backup kit at that point as well.
From what I've seen you won't be able to notice the difference unless you're using it for application data. For OS and Apps the two SSDs above will be the same speed in the native SATAII as in one of those PCIe adapters - pretty close to zero difference.
