Explaining RAID?

Nitrojan · 1 Feb 2008 at 20:29

Hey, now I know this may sound very noobish but I've heard a lot of people talking about different RAID sequences for HDD.

What exactly is RAID? Could someone please explain?

Hehe, I know it's probably noobish but if you don't ask you'll never know ^_^

Thanks,

Adam

radderfire · 1 Feb 2008 at 20:32

http://en.wikipedia.org/wiki/RAID

paradigm · 1 Feb 2008 at 20:32

Its not that simple to explain, due to differing levels of RAID setups.

Its probably easier and simpler to just read the WIKI entry

http://en.wikipedia.org/wiki/RAID

EDIT: Damn you

ins0mn1ac · 1 Feb 2008 at 20:35

http://forums.overclockers.co.uk/showthread.php?t=17366196

try that also!

Ben M · 1 Feb 2008 at 20:35

edit: sorry

paradigm · 1 Feb 2008 at 20:38

Ben M said:
more than one HDD with exactly the same stuff on it, so you can access data more quickly.

No. 100% wrong on so many levels.

It would depend on the level of RAID used.

RAID0 for instance wouldn't be even close to what you said, it allows for increased performance, but doesn't have a duplicate anywhere.

RAID5 and RAID6 would have parity shifting to deal with.

RAID1 would have a mirror, but wouldn't speed up write performance, as everything has to be written twice. Infact, RAID1 isn't for performance at all, its just for redundancy.

Get your facts straight before offering advice

jack21 · 1 Feb 2008 at 20:39

Use of RAID would be in a server where you would want to replicate data to two drives, one for backup in case the other fails. In a typical desktop, you would probably see some speed increases, but not really enough to make it worthwhile.

crazyDAJT · 1 Feb 2008 at 20:41

raid = redundant array of inexpensive discs

raid0 = speed need minimum 2 discs technically this isn't raid any redundancy
raid1 = best protection need minimum of 2 disc
raid10 = hybrid of 0 and 1 need minimum of 4 disc
raid5 = can lose one hard-drive as parity is stored across them, minimum of 3 discs

most motherboards support all these raid levels, but raid5 will suffer of writs as it not proper hardware, I would only use this if you are making a NAS box

Remember raid is not a backup solution, it only protects against hardware failure.

paradigm · 1 Feb 2008 at 20:41

Not enough to make it worthwhile?

I certainly wouldn't go back to a non RAID5 workstation.

paradigm · 1 Feb 2008 at 20:42

crazyDAJT said:
raid = redundant array of inexpensive discs

raid1 = best protection need minimum of 2 disc

raid5 = can lose one hard-drive as parity is stored across them, minimum of 3 discs

Er, how can RAID1 be the best protection if the array fails upon ONE disk failing?

Surely RAID5 (one disk can fail and array still works) and RAID6 (two disks can fail and array still works) are far superior in terms of both performance AND redundancy :/

RAID = Redundant array of INDEPENDANT disks

(originally anyway)

crazyDAJT · 1 Feb 2008 at 20:44

jack21 said:
Use of RAID would be in a server where you would want to replicate data to two drives, one for backup in case the other fails. In a typical desktop, you would probably see some speed increases, but not really enough to make it worthwhile.

personally, i think raid 0 and raid 1 are worth it, raid 0 for a boot drive, raid 1 for storage. but still not a back up solution

paradigm · 1 Feb 2008 at 20:47

crazyDAJT said:
personally, i think raid 0 and raid 1 are worth it, raid 0 for a boot drive, raid 1 for storage. but still not a back up solution

Minimum RAID0 drive (performance for your boot disk) = two drives
Minimum RAID1 drive (redundancy for your data) = two drives (ones capacity lost due to duplicate)

You therefore have 4 disks, just run RAID5 ffs :/

crazyDAJT · 1 Feb 2008 at 20:47

paradigm said:
Er, how can RAID1 be the best protection if the array fails upon ONE disk failing?

Surely RAID5 (one disk can fail and array still works) and RAID6 (two disks can fail and array still works) are far superior in terms of both performance AND redundancy :/

you can lose a disc in raid1, its mirroring, raid 5 and raid 6 are more scalable. but then its all just a question of probability the more discs the higher the chance of simultaneous fails

paradigm · 1 Feb 2008 at 20:48

crazyDAJT said:
most motherboards support all these raid levels, but raid5 will suffer of writs as it not proper hardware, I would only use this if you are making a NAS box

Suffer in writes?

I get a whole 3% processor load with my "pseudo-hardware" RAID5 array, it certainly doesn't "suffer" with writes.

crazyDAJT · 1 Feb 2008 at 20:50

paradigm said:
Minimum RAID0 drive (performance for your boot disk) = two drives
Minimum RAID1 drive (redundancy for your data) = two drives (ones capacity lost due to duplicate)

You therefore have 4 disks, just run RAID5 ffs :/

I would if i had a proper hardware controller, but are we we talking low end, i dont think Nitrojan is ready for this level of commitment

p.s. i hate this macbook Im writing on

paradigm · 1 Feb 2008 at 20:50

crazyDAJT said:
you can lose a disc in raid1, its mirroring, raid 5 and raid 6 are more scalable. but then its all just a question of probability the more discs the higher the chance of simultaneous fails

But, you need to lose HALF your storage capacity with RAID1, which doubles with each two disks you want to add. RAID5 you lose the capacity of ONE drive, RAID6 TWO disks.

RAID1 is a pretty useless RAID level when all is said and done.

Firestar_3x · 1 Feb 2008 at 20:57

paradigm said:
RAID1 is a pretty useless RAID level when all is said and done.

Totally agree, Raid5 is they way forward, given the availability of cheap or even integrated raid 5 controllers and the affordability of large SATA drives, large Raid volumes are now accessible to the masses.

oddjob62 · 1 Feb 2008 at 21:00

paradigm said:
Suffer in writes?

I get a whole 3% processor load with my "pseudo-hardware" RAID5 array, it certainly doesn't "suffer" with writes.

Wait till you see a SQL or Exchange server where someone has set up the transaction logs on RAID5.

For extremely high amounts of relatively small I/O data, RAID5 is actually SLOWER than JBOD, due to the extra calculation and write that is needed. That is why raid 10 is always recommended on these occasions.

paradigm · 1 Feb 2008 at 21:01

Ah, but that is why with a decent server setup, you have the array controller split the disks into a RAID5 array and a RAID1+0 array with small stripe size for your logs drive

Its a different scenario though.

oddjob62 · 1 Feb 2008 at 21:03

paradigm said:
Ah, but that is why with a decent server setup, you have the array controller split the disks into a RAID5 array and a RAID1 array with small stripe size for your logs drive

I'm just saying that RAID5 can have issues with writing

. And if it's a decent server it will have raid 10 not raid1