You can setup IDE drives as a RAID array. There are hardware units and also software which can be used, but I would not expect to see any performance improvement in a PC based system and you might see a decrease due to the overhead. RAID0 is actually AID, no R, and if one drive dies all is lost since the data is split over both disks.
One issue with IDE drives is that if the master dies, you will not be able to access the slave, so you could have problems depending on what the RAID unit does. If it marks both as bad, then you are done. It is best for IDE to have one drive per channel or a very good unit/software.
A RAID5 with three 100Gb disks would show up as 200Gb as a single disk.
You can still lose data, but it is much less likely. In part it depends on what you are using and how it deals with write errors and other issues. I have seen expensive units have issues where the write on one disk fails and it does not get properly dealt with since as far as the system is concerned the data was written. This meant that it was needed to read the whole array from time to time to ensure that there were no read errors. If you get a read error and then a disk fails, you are SOL.
Contrary to what was said, in a RAID5 setup, you can lose any disk without losing data since it does not need the parity or it can re-create the data with the parity. That is the whole point of RAID. The parity is nothing special really.
The decision to use RAID or not depends on how critical the data is and whether it is worth the risk of data loss. It might be possible that doing backups is enough to ensure no data loss. If you have constantly changing critical data, then it is a good idea. If you have data which you still have a copy and you can backup the data to a DVD or some other media, then it is not really needed. Use of RAID requires more knowledge since it is not 100% perfect and you need to know where the risks are and how to deal with them. Also, you are at the mercy of the manufacturer with regards to the quality and how much your data is at risk.
For example, a short time ago I was working on a system which failed a drive. I repaired the data errors (remapping), it still would not rebuild the array. I installed a new disk and it still failed. It turned out that another drive had an error which showed up when attempting to read or rebuild. After fixing (remapping) that error, I could rebuild the array with either disk. Unfortunately the system was not setup to log the errors, so the error on the second disk which unnoticed. Even if it logged the error, unless someone looked at the logs (which was not being done), you have a serious problems, especially since people think that the data is protected and that you can not lose data with RAID, which is not correct.
One thing to realize is that the RAID array will not protect against corrupt files or removal of the file, whereas a backup will, as long as you keep the backup long enough and notice the problem.
Edited by Kemasa, 20 March 2006 - 04:47 PM.