RAID, Stripping, 0, 1 Array

[Reefsmoka]

Could someone explain what Raid is in laymens terms, what it does, and how you do it. I've seen it in so many mags and stuff, but have no idea what it is! Also i'd like to know about the others Stripping, 0/1 Array.

I know its summut to do with hard drives, but thats as far as i go.

 

[Ian]

RAID ishort for Redundant Array of Independent (or Inexpensive) Disks, a category of disk drives that employ two or more drives in combination for fault tolerance and performance. RAID disk drives are used frequently on servers but aren't generally necessary for personal computers.


There are number of different RAID levels. The three most common are 0, 3, and 5:

Level 0: Provides data striping (spreading out blocks of each file across multiple disks) but no redundancy. This improves performance but does not deliver fault tolerance.
Level 1: Provides disk mirroring.
Level 3: Same as Level 0, but also reserves one dedicated disk for error correction data. It provides good performance and some level of fault tolerance.
Level 5: Provides data striping at the byte level and also stripe error correction information. This results in excellent performance and good fault tolerance.

Reference : http://www.webopedia.com/TERM/R/RAID.html

I hope that explains it a little, its the basics of it

 

[floppybootstomp]

Ian explained it pretty good there.

With RAID the hard disks are connected to a controller which performs the RAID applications. This can either be an onboard controller within the motherboard or a seperate PCI controller card.

Most commonly used is RAID 0 which is basically two disks seen as one by your OS. Ideally the two disks should be the same size, type and made by the same manufacturer. Writing to two disks as one increases performance, notably speed.

Of course if one disk crashes, even though the other is physically OK, you lose all your info. There again, if you have your OS on one HDD and that crashes, it's much the same thing.

I have two RAID 0 setups, one with two two x 35Gb Raptors, it's quite nippy, and the other with two x WD 120Gb SATA drives, giving me 240Gb that runs very well.

The other most commonly used RAID setup is RAID 1, which is basically two disks the same, one has the usual on it, the other provides a constant backup. So if main disk fails, you still have everything saved as a mirror.

If you use four hard disks you can have RAID 0 & 1 on the same controller which is the best of both worlds but a tad expensive.

Of the other RAID setups, I know nowt.

 

[Reefsmoka]

I understood that pretty well guys, thanks alot.

 

[ChristopherP]

this is the part where we argue about whether it is independant or inexpensive...

 

[muckshifter]

... or weather the Home User really needs to bother.

 

[floppybootstomp]

... or weather the Home User really needs to bother.

Well, you want the truth - yes & no

Definitely yes with a pair of Raptors. They peform in a RAID 0 config noticeably faster than a single Raptor. And I'm not just talking benchmarks here, I mean, I can really notice an improvement in performance during everyday use.

As for my other setup - the 2 x WD 120Gb SATA drives - nope, I can notice no difference, quite honestly, to that of a single drive. Only the ATTO benchmark shows an improvement.

I've tried various RAID 0 setups, starting first with a pair of IBM 20Gb IDE disks on an Abit KT7-R (remember that?) and apart from benchmarks, I've noticed no 'real life' increase in performance. In fact, the biggest 'noticeable' improvement to any system I've had (with the exception of the pair of Raptors) was increasing memory from 512Mb to 1Gb.

Apart from the Raptors, I'd imagine a SCSI RAID config would perform well, though I've never tried it, the cost of a good SCSI RAID controller card and a pair of SCSI disks is a little prohibitive.

One adavantage I have with using 2 x 120Gb drives is that I overcome the problem Windows has in recognising HDD's over 160Gb, I now have a 240Gb hard disk that Windows actually somehow still sees as 2 x 120Gb.