12-04-2006, 07:29 AM
I disagree completely (at least with the performance part. Price-wise, or on storage capacity, the Raptor is harder to defend)
First, the IDE/SATA interfaces are not the bottleneck. A good 7200RPM drive peaks at around 70MB/s. (And that's peak. It doesn't often get that high).
SATA can handle 150MB/s.
IDE can handle 100 or 133 MB/S.
So that makes literally zero difference.
What does make a difference is the drive(s) themselves.
First, the raw numbers:
Raptor:
You get 33% faster seek time and 33% more bandwidth than with a single 7200 drive.
7200 RPM in raid:
You get slightly worse seek times, and close to 100% more bandwidth. compared to a single drive.
Ok, so both have advantages that the other can't match. The question is, which is more valuable?
For most purposes, harddrives are held back by seek times. A 7200RPM drive wastes around 10 milliseconds every time it has to start reading from a new location. That's huge. (gives you 100 reads per second. In the worst case, each read is a single sector or 512 byte. So if we're reading lots of small files, or otherwise fragmented data a 7200RPM drive will be able to give you 500 KB/s if you're unlucky.)
On the other hand, the max transfer rate isn't so much of a problem. 70MB/s isn't the most amazing number but it's still quite decent. Takes around 10 seconds to copy a CD's worth of data, for example.
But it only takes a few seeks to dramatically cripple this number. And it's really hard to avoid those couple of seeks for more than, say, 50ms.
So what does that tell us?
The obvious answer is that in cases where seek time is important, the Raptor will easily outperform RAID.
In cases where the total transfer rate (or bandwidth) is important, RAID will win.
A slightly more detailed (and useful) answer would also say which cases these are... So here goes:
Let's take the latter case first. When is RAID, or more disk transfer bandwidth, going to make a difference. The answer is "hardly ever" on desktop (or notebook) systems.
Almost everything you do on regular PC's is constrained by large numbers of scattered reads, which means tons of seeks.
But where it *does* make a difference is:
- When copying big files (Especially when copying between two separate drives. When copying from drive A to drive B, you'll actually get better performance if the two are not in RAID. But if A is a raid of two drives other than B, you should be able to see a noticeable improvement)
- Uh, that's basically it. When copying big files.
That happens on file servers, in some cases on database servers, and it happens if you work a lot with video encoding or similar tasks. A RAID setup only really pays off if you move 10MB+ chunks of data frequently.
The only case where it *sometimes* can happen on a desktop PC is when loading (Windows or games). After all, that's a matter of reading a huge amount of data. Unfortunately, it's not only that. This data is often scattered between tons of small files, and if there are big files, they're fragmented. So the end result is that even here, you often won't see big improvements. In many games, RAID only improves your loading time by 5-10%. In some cases, it even slows you down.
Of course, there *are* games where loading really goes faster with RAID. No doubt about that, and in those cases you might see a 50% speed boost. But unfortunately, they're rare.
So where does the improved seek time of a Raptor pay off?
- Everywhere else, basically.
When doing regular work. When playing games, that is, in-game, not waiting for a level to load. (you tend to get occasional disk accesses. Either for the pagefile, or to load some small chunk of data. Both of these will be noticeably smoother with a Raptor)
- Waiting for a game (or Windows) to load: As said above, this sometimes benefits from RAID (in which case the Raptor still gives us a 33% improvement over a normal drive), but often, seek time is more important, in which case the Raptor *also* gives us a very noticeable improvement. (We get faster seek time *as well* as the faster transfer rate)
Basically, unless you have special needs (making a file server - not that I'd recommend RAID 0 for that. Use RAID 1 in those cases. Would suck to lose data on a file server - or frequently encoding videos or other tasks involving huge files), the Raptor will be faster. And probably more importantly, the Raptor will be faster across the board, no matter what you use it for. RAID is fast at some specialized tasks, and practically as slow as a 7200RPM drive in many others.
So, before the "RAID is l33t"-brigade can get a word in, here's a few links you might find interesting:
http://faq.storagereview.com/tiki-index.php?page=SingleDriveVsRaid0
http://www.anandtech.com/storage/showdoc.aspx?i=2101
http://www.storagereview.com/articles/200406/20040625TCQ_1.html
For the best speed in general, get a Raptor.
For the best speed on file servers or such, get RAID. Note that this will give you next to no speed boost in many other cases, unlike the Raptor.
For the most storage space, get RAID or single 7200RPM drives
And if price is a concern, you might want to stick with either RAID or regular 7200RPM's as well.
