Raid question!

[Guest]

Hi,
I was thinking to buy an ABIT RAID mobo for my new, upcoming system ( 1GHz Athlon and a Creative GeForce 2). I was thinking of buying one Maxtor 40GB HD, and also putting in my 13GB Maxtor HD I have now in my P3 500. Is it impossible to put 2 different HD's on a RAID mobo??? Or is it not neccesary to put in 2 drives?

Is there anything else I should be aware of, before I buy the RAID mobo?

Does it give a performance boost in games?

Thanks

 

[girish]

you need similar hard disks to implement RAID. RAID is used basically to improve data security. if one of the hard disk fails you can retreive your data from other(s). you can split your bytes between the two disks to improve performance. this is RAID level 0. by using the two hard drives you can also mirror your data. this is RAID level 1. you can also implement RAID level 0+1 so to say by doing it both ways. raid level 5 uses more than two hard drives and uses data stripping to store the data bits in a mathematical combination among the hard drives. should any disk fail, it can easily get it back by applying the reverse equations. high end servers implement raid for this. RAID doesnt improve the performance as such, but the reliability of your data. but it can very well optimised in such a way.

ide raid is relatively newer concept (earlier it was just scsi disks that had raid and that too on high end raid controllers like adaptec ones. this RAID mobo is one for a cautious home user who can now implement RAID at a relatively lower cost, using common IDE hard drives.

for your application, what you need is a faster disk interface, maybe you can go for a SCSI disk rather than IDE RAID. i dont think the cost difference would be much.

girish

 

[Guest]

If you're considering the Abit KT7-RAID, here's a ton of info on it:

<A HREF="http://go.to/kt7faq" target="_new">http://go.to/kt7faq</A>

Mike

 

[Bandit]

eh.. Close.. A few minor corrections. You can use pretty much any 2 hard drives in a raid setup. Keep in mind that the effect of using two different drives is that you are limiting the space of the larger one by the smaller one. To make this a little more clear, let me explain the 3 raid modes supported by the KT7 Raid.


Raid 0

or data striping uses 2 hard drives in paralel to improve disk transfer rate. Basically, the controller writes portions of the file to each disc, so that a single file straddles both discs. Then, when you read the file, you have 2 hard discs sharing the task, effectively doubling the transfer rate.

The are a couple of things to note here. The increased transfer rate would be a max of 2 times the transfer rate of the SLOWER drive. That's because no matter how fast your quicker drive is, you still need to wait for the slower drive to read it's portion of the file before it's useable.

The other issue with striping is that you can only utilize a portion of the space on the larger drive equal to the total of the smaller. Although you CAN use two different size drives, Raid requires they both be the same size. So, if one drive is 40GB and the other 13GB, raid will only use 13 of the 40GB of space on the first drive to match the second. Raid 0 however, adds the space used on both drives together, so in the above example, you would have your 13GB drive, plus 13GB of the 40GB drive, to give you a total of 26GB of space.


Raid 1

is mirroring. It is useful when there is an absolute need for data integrity. I can't really see much use for it on a PC (other than a marginal increase in access time). Basically, if one of your hard drives fails for whatever reason, the other has an identical copy of the data. This has been refered to as a "backup" in this forum, but that term is not quite correct. With Raid 1 you don't "back up" your data to a second drive. Rather, both drives read and write data at the same time, so BOTH contain your "master" data copy. If one crashes, you don't have to really RESTORE your data. Raid takes care of that for you as soon as you replace the faulty drive. In the meantime, it runs off the disc that is still good as if nothing had happened (supposedly

As far as size goes in Raid 1, you are limited to the smallest of both your drives. And they are NOT added together. In the above example, 13GB and 40GB drives used in Raid 1 would effectively be 1 13GB drive.


Raid 0+1

gives you the best of both worlds. Unfortunately you also need 4 hard drives to take advantage of this. Basically you just add together Raid 0 and Raid 1. To make it easier to understand, assume U is a hard drive, and W is a set of two hard drives, combined in Raid 0 (data striping)

U+U & U+U (Two sets of two discs Raid 0 on each set)

gives us

W+W (Each set is considered 1 drive, combined in Raid 1)

Gives us our final product, 1 hard drive Raid 0+1.

The formula for size would simply be the smallest drive of the 4. If you use 3 80GB drives, and one 5GB drive, you would have effectively 5GB of storage.


Hope this helps somewhat. Tom offered a great article on Raid when he covered converting the Promise 66 controller into a Fasttrack Raid controller.