965p-ds3 raid0 issues

Glass · 6 May 2007 at 22:01

Finally got xp installed on my raid 0 array however the array is showing the wrong size. I have 2 x 320GB disks, when i set up the array the size set itself to 640 automatically.

Windows is showing one drive at 640GB however i go into the raid bios and it says it is a raid0 array. Can someone help?

Olly · 6 May 2007 at 23:09

from what you've written that is correct.
2x320=640 (give or take after format etc)

RAID0 = drive striping, so windows will see one big disk.

Glass · 7 May 2007 at 08:03

but i thought raid 0 used both disks and effectivley halfed the availalbe space on the array?

vanandjuanunited · 7 May 2007 at 08:05

Nope. Raid 0 = sum of disks added.

Glass · 7 May 2007 at 09:11

I'm confused!

I thought RAID0 was for preformace, data was split accorss both drives. So if I saved a file part of the file would be on both drives giving me access faster read/write times. If this is so then I thought the capacity of the sum of the drives halfs? :confused:

vanandjuanunited · 7 May 2007 at 09:15

Nope it writes part of the data to each drive - thats why its faster.

A quick summary of the most commonly used RAID levels:

RAID 0: Striped Set (2 disk minimum) without parity: provides improved performance and additional storage but no fault tolerance from disk errors or disk failure. Any disk failure destroys the array, which becomes more likely with more disks in the array.
RAID 1: Mirrored Set (2 disks minimum) without parity: provides fault tolerance from disk errors and single disk failure. Increased read performance occurs when using a multi-threaded operating system that supports split seeks, very small performance reduction when writing. Array continues to operate with one failed drive.
RAID 3 and RAID 4: Striped Set (3 disk minimum) with Dedicated Parity: Provides improved performance and fault tolerance similar to RAID 5, but with a dedicated parity disk rather than rotated parity stripes. The single disk is a bottle-neck for writing since every write requires updating the parity data. One minor benefit is the dedicated parity disk allows the parity drive to fail and operation will continue without parity or performance penalty.
RAID 5: Striped Set (3 disk minimum) with Distributed Parity: Distributed parity requires all but one drive to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure. Upon drive failure, any subsequent reads can be calculated from the distributed parity such that the drive failure is masked from the end user. The array will have data loss in the event of a second drive failure and is vulnerable until the data that was on the failed drive is rebuilt onto a replacement drive.
RAID 6: Striped Set (4 disk minimum) with Dual Distributed Parity: Provides fault tolerance from two drive failures; array continues to operate with up to two failed drives. This makes larger RAID groups more practical. This is becoming a popular choice for SATA drives as they approach 1 Terabyte in size. This is because the single parity RAID levels are vulnerable to data loss until the failed drive is rebuilt. The larger the drive, the longer the rebuild will take. With dual parity, it gives the array time to rebuild onto a large drive with the ability to sustain another drive failure.

Participant · 7 May 2007 at 09:52

Glass said:
I'm confused!

I thought RAID0 was for preformace, data was split accorss both drives. So if I saved a file part of the file would be on both drives giving me access faster read/write times. If this is so then I thought the capacity of the sum of the drives halfs?

Imagine a 1MB file...
Imagine writing it to one simple SATA drive...you use 1MB on one disk, correct?

Now take half of that file and write it to one disk, and the other half and write it to the other disk. You've used 500KB on each disk, total usage is still 1MB.

D'accord?

Glass · 7 May 2007 at 10:05

doh!

Thanks for the info, raid1 halfs the drives as it mirrors, I assumed this would happen with raid0 to.

Trippynet · 7 May 2007 at 10:05

I think you're confusing bits of it with RAID 1 (mirroring). This will use 2 disks and give you only the capacity of one disk to play with as it saves 2 copies of each file. RAID 0 only saves one copy (split across both disks), hence the entire space of both disks is available to you. RAID 0's biggest downside is that if either disk dies, you lose everything and so implementing some form of backup solution is a very wise idea.

IAmATeaf · 7 May 2007 at 14:28

Don't want to sound like an arse

but if you've not done any reading into RAID then it may not be for you especially if there are problem in the future.

Remember that in RAID 0 if a single drive dies in the RAID pack then you've lost all the data on the pack. Most people would have a pair of small drives on RAID 0 just for the OS so if it dies then then you can quickly repair and reinstall the OS. I'd never personally put any important data on RAID 0 unless there were good backups of it done at regular intervals.

Glass · 7 May 2007 at 14:54

I read the shoot out between a raptor and two drives in raid0 on tomshardware, the article appealed to me as I could get just a good preformace for cheaper. I'm aware of the issues of disks failing in raid0 however I've got a third disk which will act as a backup drives.

The system I've just built is a test bed for a friend who requires a video editing workstation. I hope to have all issues ironed out when it comes to buliding his.

Olly · 7 May 2007 at 19:19

well, to complicate things more then, if you have 3 disks, why not do RAID5 ? all the benefits of RAID0 but with fault tolerance. ( if one drive fails the others just keep going with no loss of data !)

quantumisation · 8 May 2007 at 00:05

cause then hed have to buy a raid card

ByteJuggler · 8 May 2007 at 02:09

Olly said:
well, to complicate things more then, if you have 3 disks, why not do RAID5 ? all the benefits of RAID0 but with fault tolerance. ( if one drive fails the others just keep going with no loss of data !)

RAID5 typically is nowhere near as fast as RAID0 (even though it is typically faster than a single disk providing you've got a reasonable controller.) To however not feel short changed performance wise with RAID5, you need a really fast dedicated hardware RAID5 controller, which typically will cost a lot of money as such controllers are typically targetted at the server market.

Glass · 8 May 2007 at 11:05

If raid 5 were as fast as raid 0 I'd go with it. However I am looking for preformace at a good price. I'll have to take my chances with a raid 0 array and make sure I provide a backup solution.