View Full Version : RAID array - 1 or 5?

23-04-2003, 10:02 AM
I cannot decide which RAID array is better to use, 1 or 5. I want one that is easy to handle, and doesn't require more than four drives.

According to these documents:
RAID 1 (http://www.acnc.com/04_01_01.html)
RAID 5 (http://www.acnc.com/04_01_05.html)
RAID 5 is good for database, internet, intranet, and email servers.

However, it also says it is complex, disk failure has a medium impact, and is relatively difficult to rebuild.

On the other side of the fence, RAID 1 is extremely inefficient, hardware implementation is recommended, and isn't recommended for use in a webserver.

Can anyone tell me which way I would be better to go, or a completely different solution. Also, I plan to use SerialATA drives, unless they are too expensive (last prices I saw, they were around $1000), in which case I think I'd go for SCSI.

23-04-2003, 10:43 AM
Raid 1 has no fault tolerance and thus if one drive fails, data is essentially lost

Raid 5 has fault tolerance and thais if one drive fails, data can be rebuilt.

Raid 10 has fault tolerance with striped mirroring. Essentially indestructable.

SCSI drives provide superior preformance in RAIDs than IDE drives

Since you do not describe the appliacation for the RAID - and whether it is hardware or software - the discussion becomes vague and whimsical


23-04-2003, 11:19 AM
Well actually in practice hardware RAID 1 is a good performer, same speed writes as a single disk, potentially twice the read speed. RAID 5 wont perform so well with writes as it needs to write parity data, but reads are good.

I don't know what it's talking about regarding 'difficult' to rebuild. Modern hardware RAID is idiot proof; -just pop the disk in and let it go. Don't waste you time mucking round with software RAID. It's rubbish.
Serial ATA won't perform any better than IDE at the moment, wait for SAS or go straight to SCSI.

Personally I would suggest a 2 channel Ultra 160 SCSI RAID controller with 5 disks. Set up a Mirror (RAID 1) for the OS on 2 disks on first channel, and a RAID 5 set on the remaining 3 disks for data/database etc on the other channel.

I wouldn't bother with ultra 320 with only 5 disks though.

23-04-2003, 11:24 AM
just to correct merlin here......

The Levels 0 and 1 are as different as fire and water; Level 0 actually exposes your data to a higher risk, while Level 1 ensures maximum security. If you want both, you'll find yourself having to dig deep into your budget. RAID Levels 3 and 5 store parity information so that, in case a drive crashes, the entire data stock can be recovered once the culprit has been exchanged. However, it takes a rather powerful processor to calculate these checksums - the best choice would be an RISC model (Reduced Instruction Set Computing), because these chips have been optimized for their tasks. The appropriate controllers are expensive, and you'll need at least three hard drives.

raid 0 stripes data onto both drives. basicly it can read/write data to both drives at the same time making it faster than a single drive. however if one drive dies all the data is lost.

raid 1 mirrors the data on 2 drives so if one drive fails the other still holds the complete data. advailable on software raid cards but very few onboard raid cards.

raid 5 uses minimum of 3 drives. it calculates a parity bit so if one drive dies it can use the remaining data + parity bit to restore the data. however this requires a hardware raid card.

have a look here (http://www6.tomshardware.com/storage/20020830/ide_raid2-01.html)

23-04-2003, 11:24 AM
The idea is for a webserver, handling ASP pages and a database.

23-04-2003, 02:02 PM
Raid 10 or Raid 5 with scheduled backups

23-04-2003, 02:22 PM
Will investigate further.

Thanks for the help.