RAID??????

deadlock-777

i know about certain areas of pc categories but you cannot know it all [thats the beauty of the subject]i know about cpu,s stepping ,graphics cards ,ram ,hard disks and so on but i never have bothered with this thing in my start up menu called RAID.can someone please tell me basically its function and a good link to take me for whatever itis that it does.please o masters of the disc array know its a basic question so i hope others will benefit from the responces:)

kryyst

Essentially what a RAID does is treat multiple disks as one 'drive' the advantage to a raid is that because multiple disks are being accessed at once it can generally get to the data faster, because instead of doing 2 sequential reads from 1 drive it can do two parallel reads from 2 drives. The other way a raid can be deployed is to create redundancy. So you have 2 drives set up in a mirrored fashion or 3 drives setup where aprox 75% of the data is mirrored. So if you loose one drive, you still keep all the data. That's the point of raids in a nut shell you then have various types of raid 0, 1, 3, 5 0+1 etc... that all do various versions of the above to obtain a desired result.

Personally for what it's worth in a home computer you generally will benefit more from keeping all your drive space and not creating a raid.

Snarkasm

To go slightly more in-depth:

RAID 0 is what's called a striped setup; your drives are linked together so they look to your OS like one big drive, and when data gets written to or read from the "drive," it's actually being read from two drives at the same time, which gives you the speed boost kryyst mentioned. The downside to this is if you manage to corrupt your array, or a drive starts failing, you have zero redundancy, and you lose everything you stored in that setup.

RAID 1 is called a mirrored setup; your drives are exact clones of one another. This has the side effect of potentially slowing down your write times compared to RAID 0, since you'll be writing the exact same data to two different drives, but I don't think it has any effect on your write times vs just a single-disk setup. The read times also remain the same, as the OS only reads from one drive, since the same data's on both.

Various other flavors, like 0+1, 5, 10, and JBOD exist, but many of these are very impractical for home use and require many hard drives; JBOD stands for just a bunch of disks where you just pool all the storage into one massive drive. Many people will tell you that for home use, no RAID is practical, but at that point, it's really just personal preference.

In all these situations, you're best suited by using two drives of at least the same capacity, if not the same exact make and model. RAID generally only works if the two or more drives have the same amount of space to play with.

I run two Raptors in RAID 0 from way back in the day, and all it does is make you learn to keep biweekly backups. If you're going to go that route, just know the consequences, be careful, and do whatever you feel suits your desires.

Thelemech

:bigggrin:... well this post was far easier to decipher!!

http://tldp.org/HOWTO/Software-RAID-0.4x-HOWTO-2.html

the_technocrat

..and even easier (RAID levels in pictures)

http://www.acnc.com/04_01_00.html

Your-Amish-Daddy

I have to agree with everyone here in the sense that raid would have no benefit to the average Joe Shmoe-desktop pwner. All I've really got is my raid tools running, checking on my non-raided discs. Raid0 has the best performance I've seen due to the ability to put data on separate drives. The only reason I could see a Joe Shmoe making a raid is if he has a bunch of smaller drives, and just needs the larger storage but doesn't care about the risks of the data.

In my humble opinion, the only really useful raid would be Raid 0+1, since I move alot of data, but I don't always have a means to back it up during a failure of some kind.

deadlock-777

thanks mate...sorry if i go on.thanks to everyone for giving me these informative replys .

mas0n

Your Amish Daddy wrote:

I have to agree with everyone here in the sense that raid would have no benefit to the average Joe Shmoe-desktop pwner.

I must disagree, I think RAID 1 is very useful for average users. Granted, it does not protect from the most common cause of data loss (user error) but it still serves it's purpose. HDDs are so cheap that "losing" the storage space is no big deal and contrary to what MJancaitis said about RAID 1 read times, a quality RAID controller will offer MASSIVE improvements to read performance in a RAID 1 array. And for the average user, read performance is what really matters.

Snarkasm

How's that, Mason? Do the better controllers read from both disks simultaneously?

If so, apologies, I was basing it off of older tech, I guess.

Kwitko

With a good hardware controller, RAID 1 will read the data from both drives at the same time. Think of it this way:
When you read data from a non-RAID drive, it reads sectors 1-10 for your file. It has to read each sector one at a time, there's no way around it. It can read the sectors out of order, but it still can only read one at a time. With RAID 1, the same exact data is on two physical drives. The controller can read sectors 1-5 from drive A and sectors 6-10 from drive B, thus dropping the read time in half.

mas0n

MJancaitis wrote:

How's that, Mason? Do the better controllers read from both disks simultaneously?

If so, apologies, I was basing it off of older tech, I guess.

No apologies needed here, hope I didn't come off as condescending. The rest of your post was spot on and what you stated about RAID 1 is mostly true for the average user who will use the controller integrated into their motherboard.

Your-Amish-Daddy

Oh yeah and some of the better raid controllers can actually teach the heads to write in a certain way (Sequential writing) so that all the data can be read about 20% faster than normal.

kryyst

mas0n wrote:

I must disagree, I think RAID 1 is very useful for average users. Granted, it does not protect from the most common cause of data loss (user error) but it still serves it's purpose. HDDs are so cheap that "losing" the storage space is no big deal and contrary to what MJancaitis said about RAID 1 read times, a quality RAID controller will offer MASSIVE improvements to read performance in a RAID 1 array. And for the average user, read performance is what really matters.

Going to have to disagree - average users - definitely won't notice an improvement worthy of the cost and potential headaches. Technically faster is a far cry from noticeably faster and the average user isn't going to notice. They'll get a more noticeable speed increase from defraging their harddrives and turning off indexing.

Where you'd notice an improvement from raid is if you are doing I/O intensive apps, like database work, file servers, and multi-media production. Most games don't see a huge benefit from a typical home raid setup nor do most typical apps.

Furthermore most average kiddies that are using their machines to download movies and play games would be further served from a non-raid 1TB storage system then a 500gb raid system, specially one built off of your normal stock raid controllers. I'm not dissing raid. Just nothing I'd recommend to someone who doesn't know what it is, nor fully understands why/when you'd want to use it.

Also people put this concept out that raid protects you from data loss, which is true if that data loss is a failed harddrive. Most data loss is not based on harddrive loss and a raid won't protect you from that at all. If you have money to burn, and can dedicate a drive to data backup, then put a second drive as a backup drive. Not a mirrored drive but an actual backup drive that uses software to backup the data. That is a much better use for an average user if you want to put some money to use to protect yourself.

Leonardo

In my humble opinion, the only really useful raid would be Raid 0+1, since I move alot of data, but I don't always have a means to back it up during a failure of some kind.

Listen to this guy. He's right.

In my humble...

Almost quit reading after that phrase!



j/k