On Sun, Dec 31, 2006 at 19:48:23 -0700, "Ashley M. Kirchner" <ashley@xxxxxxxxxx> wrote: > > I'm looking at setting up a RAID system for doing video work. My > two main requirements are speed and reliability. Speed is an issue > because of the constant streaming of hundreds of megabytes, if not > gigabytes of data that is inherent with video. And obviously > reliability, I want to make sure I don't lose any data of a drive > crashes on me. This will also be a hardware RAID solution (as opposed > to software) and, depending on funds, I may try to make it a > hot-swappable system. > > Based on all the different RAID levels out there, what does the > collective suggest? 1? 3? 5? 0+1? Raid 5 is generally good for mostly read situations, though you may want to do some bench marking to see if you really need that. More spindles are better than fewer spindles. Normally you would use raid 10 in preference to raid 0+1, since raid 10 handles failures better. If are capturing video and not publishing it, than raid 10 is usually better than raid 5 unless you have a fair number of spindles. I wouldn't be too quick to dismiss software raid. Generally unless you spend good money to get a raid card with battery backed cache, you are better off with software raid. In your case you might have a cpu bottleneck depending on what processing you are doing of the video. In that case you would be more inclined to go with hardware raid, but you would want to look at the cost of buying more cpu versus the cost of a better raid card. You should be able to rough out some numbers to see what you need to do what you want. You should be able to figure out what data transfer rates you need and then test the bandwidth for individual disks to get an estimate of how many spindles you need. And you should be able to compare that to the bandwidth supported by the controllers you are considering. If you have really heavy demands, you may need multiple controllers. Be careful with the write cache settings of your drives. If you are using software raid, you can leave write caching enabled if you use write barriers. A good raid card should properly handle write caching for you, but you might want to do some sanity tests to make sure that writes aren't being reported as complete when they are actually just in the drives' cache.
