Raid?

[freak]

Ok this may seem like a stupid question but what exactly is raid I think i have an idea but im not sure could some one go into detail on what it is and the diffrent types... And also how it works
Thx

[Virtualbody1234]

http://www.google.ca/search?q=what+is+raid...F-8&hl=en&meta= (http://www.google.ca/search?q=what+is+raid&ie=UTF-8&oe=UTF-8&hl=en&meta=)

[freak]

lol thx but im still not understanding it 100%. Ok say i had 2 hard drive on raid 0 what would be the point? Does it basicly merge the drive so the computer thinks its one drive and spread the info between the 2?

[tesco]

Originally posted by freak@26 April 2004 - 18:32
lol thx but im still not understanding it 100%. Ok say i had 2 hard drive on raid 0 what would be the point? Does it basicly merge the drive so the computer thinks its one drive and spread the info between the 2?
there are two types of raid. 0 and 1. I always get confused with the name so i cant say which is which...

but one of them, is like a security thing, the info is written to both drives at the same time so that if one drive fails the other will still be working and you wont loose ur info. two drives are required.

the other one, is for performance, both drive will spread teh info between them, so theyre both reading to open a file, and it in theory opens twice as quick. 2 drives is required to do this.

the last way, is to have a 0+1 aray, where u need four drives, and they work together to give u double the performance, and the security of it backing up the info...


well thats my attempt at explaining it, and im sorry that I dont know which one is 0 and which is 1, but i tihnk u can find that out your self.

and there are also other types of raid, but these are the most common ones.

[Virtualbody1234]

Originally posted by freak@26 April 2004 - 17:32
lol thx but im still not understanding it 100%. Ok say i had 2 hard drive on raid 0 what would be the point? Does it basicly merge the drive so the computer thinks its one drive and spread the info between the 2?
Yes, that's exactly raid 0. The drives are 'merged'.

Makes for faster performance.

[j2k4]

Originally posted by Virtualbody1234+26 April 2004 - 18:55--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Virtualbody1234 &#064; 26 April 2004 - 18:55)</td></tr><tr><td id='QUOTE'><!--QuoteBegin-freak@26 April 2004 - 17:32
lol thx but im still not understanding it 100%. Ok say i had 2 hard drive on raid 0 what would be the point? Does it basicly merge the drive so the computer thinks its one drive and spread the info between the 2?
Yes, that&#39;s exactly raid 0. The drives are &#39;merged&#39;.

Makes for faster performance.[/b][/quote]
Think in terms of entering your larder to gather ingredients for an intricate meal; you can grab more stuff faster using two hands than you can with just one.

I haven&#39;t built my dream machine, yet, but when I do, It&#39;s gonna be RAID 0/1, with the biggest SATA drives I can afford.

Securlty and performance; that&#39;s what I want.

[clocker]

Originally posted by j2k4@27 April 2004 - 07:27


Securlty and performance; that&#39;s what I want.
How very Republican of you...

[lynx]

There is also Raid 5 which needs a minimum of 3 drives.

Each block of data is divided over (n-1) drives and a checksum calculated for the nth drive. Each drive takes it in turn to hold the checksum for a block.

For 4 drives it ends up looking like this:



Drive&#58; &nbsp; &nbsp; 1 &nbsp; &nbsp; 2 &nbsp; &nbsp; 3 &nbsp; &nbsp; 4
Block1 &nbsp; &nbsp; 1 &nbsp; &nbsp; 2 &nbsp; &nbsp; 3 &nbsp; &nbsp; c
Block2 &nbsp; &nbsp; c &nbsp; &nbsp; 1 &nbsp; &nbsp; 2 &nbsp; &nbsp; 3
Block3 &nbsp; &nbsp; 3 &nbsp; &nbsp; c &nbsp; &nbsp; 1 &nbsp; &nbsp; 2
Block4 &nbsp; &nbsp; 2 &nbsp; &nbsp; 3 &nbsp; &nbsp; c &nbsp; &nbsp; 1
Block5 &nbsp; &nbsp; 1 &nbsp; &nbsp; 2 &nbsp; &nbsp; 3 &nbsp; &nbsp; c
...

You get the advantage of striping the data over n-1 drives plus the security of being able to rebuild any drive from the info held on the other drives.

The disadvantage is that in order to update only one part of a block your system has read all the drives and recalculate the checksum, then rewrite drive with the modified part and the drive with the checksum. But that&#39;s not as bad as it sounds since it is likely that the data from the other drives is already in the controller&#39;s cache, and in order to have the security you have no choice but to write to at least 2 drives.

Unfortunately, not many raid controllers support this option, mainly because they don&#39;t support more than 2 drives.

[zapjb]

clocker&nbsp;
Posted: 27 April 2004 - 09:03

QUOTE (j2k4 @ 27 April 2004 - 07:27)
Securlty and performance; that&#39;s what I want.

How very Republican of you..


And a tax write off. :lol:

[Amarjit]

There are 11 variants of RAID, or "levels" as they are commonly made a referral to.

RAID-0 is a common implementation of modern PCs, supplying a configuration of a Stripe or Mirror array - allowing for data to be secured, should there be an event of emergency, or merely for convienience - made a provision by its speed benefits.

[racer II]

http://www.acnc.com/raid.html ;)

[j2k4]

Originally posted by clocker+27 April 2004 - 08:03--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (clocker @ 27 April 2004 - 08:03)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-j2k4@27 April 2004 - 07:27


Securlty and performance; that&#39;s what I want.
How very Republican of you... [/b][/quote]
Yes. :D


Lynx-

The article which sold me on the idea had the goods (controller-wise, and reasonably priced, as I remember) for a 0/1 configuration with 4 drives.

I&#39;ll a bit rushed at the moment, but I&#39;ll try to run it down later. ;)

[atiVidia]

raid+SATA = kick@ss combo. my friends DFI board has raid 1.5. lol its 2 SATA drives (200 a piece) and theres an effective 200 gigs of capacity. raid0+raid1 on only 2 drives...


http://img8.imageshack.us/img8/7114/sdgsdgf.gif

rofl it took me a while to figure it out too... supposedly offers better protection...

[lynx]

You can do a form of raid 0+1 with only 2 drives. Since with raid 1 both drives are exact copies, it is possible to read block 1 from the first drive and block 2 from the second drive and achieve the added benefits of raid 0. However, it is relatively expensive since half the disk capacity is required for recovery purposes.

Looking at some practical exmples, for 500GB of data you would need 4 250GB disks for R0+1, with raid 5 you would only need 3 disks; but the extra cost of the R5 controller (about &#036;115 vs &#036;70 for R0+1) may make this option less attractive. If the requirement increased to 750GB of data, raid 0+1 requires 6 disks (probably requiring expensive SCSI controllers and disks) but raid 5 still works as it only needs 4 disks.


There are 11 variants of RAID, or "levels" as they are commonly made a referral to.
Raid levels 2, 3, 4, and 53 are all considered redundant.
Raid 6 is expensive to implement and only really used in very high availability, high redundancy non-stop systems.
Raid 7 is proprietory.
Raid 10 is effectively the same as raid 0+1 but is implemented slightly differently and therefore requires multiples of 4 drives. Raid 0+1 is often misnamed raid 10.

Having dealt with the oddballs, you can see that for practical purposes there are 4 commonly used raid levels - 0, 1, 0+1 and 5.


http://www.acnc.com/raid.html
Useful as a definition of the various levels, but some of the diagrams are wrong and conclusions are wrong. For example on raid 5, what happened to blocks E0, D1, C2 etc? In actual fact there are no "E" blocks.

Sorry if I&#39;ve gone on about this, you&#39;ve picked one of my specialities. :lol:

Edit: got broken off while I was posting that, so atiVidia&#39;s post wasn&#39;t there then. He&#39;s got that exactly right.

[j2k4]

Good on the both of you.

My understanding deepens; hopefully my pockets will catch up.

What kind of sucks is that my next purchase will almost certainly be a laptop, and my dream machine will have to wait.

If the opportunity comes to pass, lynx, I&#39;ll pick your brain, okay? ;)

[freak]

lol thx for all the info guys. i got it now... sorry for the late reply dsl was down for awhile