I still do not understand about RAID 0/1

So, I heard a lot that RAID improves HDD performance and stuffs. but how does it work ? Do I need 2 HDD to use RAID ? and also, I heard that RAID 1 is doing a mirror of the first HDD on the second HDD. So does RAID do backups ? as well as increase performance ? and what does RAID 0 does ?

Sorry for asking so many questions, but I'm really curious about RAID stuffs, I've been looking online for answers but I need a proper answer from the experts here. I want to try using RAID but I have too much files on my HDD and don't want to mess with that and lose my important files.

Thanks for the help

 

you need 2 HDDs to use the RAID arrays. the controller links the 2 HDDs to become one, so files will be written half to disk 1 and the other half to disk 2 (RAID0). if im not mistaken its called striping. since the writing and reading are done in parallel, of course it improves performance. however, if one half of the file was written wrongly, the whole file would be gone. RAID1 uses mirrors, which means there are 2 exact whole copies of the same file written to the 2 HDDs, unlike RAID0 which writes half of it. the advantage of RAID1 is that should one of the disks go bad, the whole file is still safe on the other disk.

hope it helps

 

loath as I am to recommend *anything* from wikipedia, their raid write up is actually pretty decent. there are also a pile of external links there for additional reading.

 

it definately helps a lot, I understand a lot better now.

so, they both do almost the same thing and it looks like RAID 1 is safer to use but why people are still using RAID 0 ? is it because better performance ?

Do I need both HDD to have the same capacity ?

 

They don't do the same thing. Raid 0 increases performance at the expense of data security, Raid 1 increases data security at the cost of halving your storage space. Never put any data you would mind losing onto a Raid 0 array.

It is best to use identical drives for any RAID, though it is possible to use ones that aren't similar.

You really sound like you shouldn't be messing with RAID.

 

Why does he not seem like he has the capability to set it up and use it? It is simple enough to set up, all you need to do is understand, which is what wikipedia is for. It has great articles on most basic aspects of anything computer related. It isn't like you need to write custom controllers or firmware yourself for the HDD's.

 

Personally, I think RAID5 is the best choice, as you get striping for speed and parity for data security, except you only need to devote 33% of your total HD space to parity instead of 50% like with RAID1 mirroring. The data recovery rate with RAID5 isn't 100% in a single drive failure like with RAID1, but it is damn close (above 95% at least).

 

uhm what? raid5 recovers one disk 100%. else it would be useless. the only danger is, when you have a lot of disks together in raid5, chance to have another one die during the restore starts to get big.

 

Thanks for the answers guys, I'm fully understand about RAID now.

 

Yeah, the advantages and disadvantages of RAID have been discussed and debated for years and years. Never hurts to reopen the discussion.

 

Isn't the chance of losing your data the same as on a single HDD installation? Obviously RAID 1 has security but for all those that only use a single HDD isn't the risk the same? I am really curious about this as I am seriously thinking about setting up a RAID 0 in my new computer.

 

look up the mttf formulae for the various raid implementations.

The more drives you have spinning, the GREATER the likelihood of any given failure.

 

Well, you've got the added factor of the raid partition and/or the controller crapping out on you.

But they aren't significant factors IMO.

 

Not at all, no. If there is a 50% chance of either drive being bad, there is a 75% chance of the array crapping out. See what I'm getting at? The chance of a failure is almost double for a RAID 0 array of two disks over a single disk. They each have a chance of being or going bad, compounding the risk. Add to this other factors like the controller or a writing error that can scrap the array. I'm not saying that there is a high probability of failure, though there can be, but a RAID 0 array is not how you want to store any valuable information.

 

Understood. Thanks Guys. Damn! Just when I thought it was safe to go back in the water ....... I was thinking of putting a couple of the new 160GB Intel X-25M drives in Raid 0. I probably still will but I will have to review my back up frequency.