What RAID level to use?

[penamty]

What would be the ideal RAID level for a computer whose most demanding use would be video capture, edition and storage? This is a small home office PC, so money is tight.

I am looking for at least the same read/write performance as with a single modern ATA hard disk at 7200rpm and UDMA 5, but with good reliability in case of disk failure and acceptable storage efficiency.

I have been checking the line of Promise Technology RAID adapters, specifically the Promise FastTrak SX4000 4-Channel Ultra ATA RAID 5 Host Adapter, but some people say that due to distributed parity, degradation can be substantial after a disk failure and during rebuilding.

I don’t know if it’s a good idea to use the same RAID for capture and storage, but I would prefer to do so since most RAID levels with the above characteristics require a minimum of 3 disks, and I plan to use a 20GB disk exclusively for the operating system, so if were to use another disk for capture that would make 5 disks, and I would need to replace the case an power supply also.


Any comments will be appreciated

[sterno]

You probably don't need RAID for that. If you really want RAID you might be best off with your 20GB for the system and applications and a RAID0 stripeset just for capture and scratch space.

RAID5 is probably the best for general storage, but most IDE-RAID controllers either don't support RAID5 at all or they have poor performance. Decent RAID5 performance during writes or during failure/rebuild requires a lot of processing power on the card, and that costs money. Decent IDE-RAID performance also requires using only one drive per channel, and a lot of the cheaper cards only have two channels.

Yes, you take a performance hit with RAID5 when you have a disk failure because it's recreating the lost data on the fly. RAID1 doesn't have that performance hit when a drive fails, but you take a hit on writes because they're done twice and you have to buy more space to get the same storage. RAID0 is the fastest, but if any drive fails you lose everything.

[penamty]

My main concern is data protection in case of disk failure, but without an impact in video capture performance. I would be happy with the same performance as when I capture to a single disk, but with the added security of knowing that if a disk fails I will not lose stored files.

What would be your best cost efficient recommendation?

[Solarjetman]

Well, if ALL you want is to protect from failure, RAID 1 will do the trick. Basically all that does is copy bit for bit the same thing to each drive. If one fails, you will have an identical copy. The speed should be pretty much the same as using a single drive (you do write twice, but its at the same time so there is very little slowdown). Any RAID card should handle this, it is the most simple implementation of them all. If it does not, you do not want to buy it, regardless of what level you use.

For an increase in both speed and data protection, RAID0+1 pretty much can't be beat. But that takes 4 drives. RAID5 is sort of a compromise between RAID0 and RAID1 as it requires only 3.