Sorry to be slightly OT and ask a dumb question
There are no dumb questions, only dumb answers. Asking questions is a good thing.
, but can anyone refresh me as to how fast the modern southbridge bus is? Basically, I mean, I've got 6 SATA2 ports on the intel controller on my board, so a modern SSD should saturate the SATA2 at 300MBps? So if I have two of those drives in RAID 3+, do I get a full 600MBps? What would be the general calculation for southbridge bandwidth? Or is it totally vendor-specific? Or is the whole system bus the same speed/width, and everything shares?
It mostly depends on two things: the amount of Flash chips, and the speed of the controller(s). If you double the amount of Flash chips, you double the throughput, as long as the controller(s) can keep up. And you can add multiple SSD drives, which basically do the same to the south bridge.
But you need very big and fast SSDs to saturate 300 MBs. 200 MBs for a single, fast SSD drive is a good benchmark.
Anyway, I've never had an SSD, been waiting for the market to adjust. Are they really awesome? Like equivalent to that money in beer awesome? And Would a 2 drive RAID setup be that much more awesome? And would it be worth getting a SATA3 card for that additional headroom?
For now, SATA2 is sufficient. They are as awesome as they are not because they're very fast at sequential transfers, but mostly because they have a neglectible seek-time. While a regular hard disk counts access times for each non-sequential sector in milliseconds, an SSD counts those in nanoseconds. Reading a lot of small files (or a large one on a fragmented disk) is just as fast as reading a single, large, (non-fragmented) file from a Raptor.
Windows pops up in 15-30 seconds after turning on the computer, applications start and are ready as soon as you click the shortcut.
But they don't help much (if any) if you load a large document or game level from a freshly defragmented drive.
It's just been a long time since I seriously considered MB architecture, and at that time there was the 100Mhz/64 bit bus, double that for RAM, X whatever for CPU, and whatever the AGP bus multiplier was. But obviously much has changed since then.
SATA is really cool and works very well for anything available in the consumer space, as long as you don't consider the extremely badly designed connectors.
The main thing to consider for SSD drives isn't SATA or the chipset, but the support of TRIM if you use Windows.
A drive has no notion of the usage by the file system, it doesn't know if a logical cluster (4-64k) is empty or in use. And it uses pretty big physical sectors (like, 512k). So, if you change a byte, the OS writes a new logical sector (512 bytes), the file system writes a cluster (4k or more) and the SSD has to write a physical sector of 512k. Which means, that the SSD has to relocate 508k of other data as well (with a cluster size of 4k). And the amount of write cycles is limited to ~100,000.
So, unless that SSD tries to write all sectors equally, defects occur. Which means: just about every write requires a reallocation of up to 512k of data.
Sectors are deleted as a whole, but can be written per block (4k or sometimes even smaller). If a sector is full, the best the SSD can do is mark a block as deleted and move it, until it runs out of free space. After that, it has to compact and move whole 512k sectors for each write of even a single byte, to make room.
Linux has a native Flash file system. Most SSD drives (except the old or Intel ones) even use a microcontroller (ARM, most likely) that runs a custom Linux kernel with such a file system, with the Flash chips in a RAID configuration. (Exactly like most RAID controllers for Windows servers.) And that works fine, as long as the host OS recognises that and tells the SSD which logical sectors are empty and can be overwritten.
That requires the TRIM command, which simply tells the SSD: this sector is empty. Which is a new addition to Windows 7.
Under Linux, you don't actually need SSD drives as such, as the OS is quite capable of using any Flash memory available directly as part of the file system. But most people use Windows.
