Raid Speeds 2 HD's v 3 or 4

[Guest Byron]

Are 2 SATA drives in raid 0 faster then 4 SATA drives in raid 0?

 

i.e, what is faster here:

 

2x74g WD Caviar HD, raid 0 stripe

 

3x74g WD Caviar HD, raid 0 stripe

 

4x74g WD Caviar HD, raid 0 stripe

 

Thanks!

[Frallan]

4 is slightly faster but MUCH more unreliable.

 

Also look at the Hitachi SATA-2:s they Rock seriously in RAID0.

[Guest Halvis]

I noticed that Angry_Games had used 3 Hitachi 80 sata2's in his (much appreciated) "quick tutorial on setting RAID-0 on the DFI Nforce4 Ultra-D or SLI-D/SLI-DR"

http://www.angrygames.com/nf4raid-1.htm

 

I was wondering if 3 were FASTER in striping than 2, or if he just wanted the extra capacity?

AG? Anybody?

[Snook]

AFAIK the more drives you have in the array the faster the setup is.

 

Somone maybe be able to elaborate a little?

 

Snook

[ccone]

In general with any striped RAID setup (RAID 0, and RAID5 for example) ... the more disks the better the performance. (though the differente is probably not noticeable without using a benchmarking tool past the 2nd disk for a RAID 0).

 

The logic is this:

 

In a striped array, the data being written to disk is split up and written to many disks. The writing and reading of the data can be done simultaneously on each disk... so if 1 disk can write/read 1 MB per second, a single disk will take 1 second to write/read that data... 2 disks would only have to write/read .5 MB each... thus cutting the time required by the array in half.

 

As a note, this only applies to the time that is spent waiting for each drive to handle the data... not the overhead added by the controller, OS, system bus, etc.

 

Bear in mind that a RAID 0 array has no hardware redundancy built in and no method to recover from a failed disk. Even if you have a 10 disk RAID 0 array, if any 1 of those disks fail, the array is destroyed and completely unrecoverable. Obviously, as you add disks, you increase the probability of having one fail, so the bigger your RAID 0 array, the greater risk you run of losing all data on that array.

 

If RAID 5 were an option for any of our integrated controllers, it adds parity information into the array as well. This takes up space (roughly one hard disk's capacity), but allows you to keep running with one disk failed/missing and to replace that disk at any time without losing any data. As a result, RAID 5 arrays must have at least 3 disks and the more the better. Since you lose 1 disks capacity to the parity information, the higher the nuymber of disks, the lower the percent of that total is used for parity. A RAID 5 array handles data reads as fast as a RAID0, but data writes a little slower because when writing it has to compute a parity stripe that can be used to reconstruct the data for a missing disk in the case that one fails.

 

 

Probably more info than you needed... but It's nto often I can talk about stuff I know (there isn't much that fits that description )

 

 

CC

[Jadawin]

But after a certain point, the access time is just as important, because the data is scattered all over the disk usually... and raid doesn't help there at all, the access time is still the same, no matter if you have 1 harddisk or 100 striped

[Guest burningrave101]

The biggest increase from RAID0 is with two drives and adding a third or fourth drive only gives a small increase in performance. That said RAID0 has very little benefit for a desktop user to begin with. Unless your transferring large files back and forth all the time then you'll see almost no benefit of it over a single 74GB raptor. If you will check out benchmarks for RAID0 arrays you'll see the system boot times and game load times are almost always the same as a single drive or within 1-2 sec. Thats hardly worth the cost of two 74GB raptors. Buy one raptor and the spend the rest of the money on a much larger storage drive.

[Fire-N-Ice]

I'd say you'd get an advantage of 2 drives, but a 3rd or 4th will only be adding very little if any. I would think the more it has to be split up to be saved, then going across many drives to gather the data, the more the processor will have to be used.? So maybe not as much to gain there. My next investment will be a small scsi for the OS, and my fav. game at that time.

[Guest Halvis]

OK, Thanks for the responses! I was going to add a 3rd, but I think I'll stick with the 2 now.