Stephen, Let me say up front that most of my (work) experience comes from SCSI. But the principles hold for ATA drives as well.
One thing that is unique to ATA drives is the fact that you get only 2 disks per channel - one master and one slave. It is also my understanding that that IDE based disks start a request and keep the channel tied up until that request is finished. On SCSI drives a request is issued and the disk can "disconnect" from the SCSI bus until is ready fulfill the request. So SCSI systems have a real advantage there. RAID: In general, the two primary modes of RAID used in businesses are RAID 1 (Mirroring) and RAID 5 (striping with parity). The reason for this is data protection. RAID 1 has some advantages in terms of write performance over RAID 5. Conversely, RAID 5 can have some read performance over RAID 1. Many people pick RAID 5 over RAID 1 because it uses their disk resources more efficiently in terms of storage capacity. Let's take 4 disks. If you protect your data using RAID 1 you will be mirroring and you will get 2 disks worth of total storage capcity. If you use RAID 5 you can get 3 disks of total storage capacity. RAID 1 has some advantages in terms of what has to be done when the disk set needs to be rebuilt following a disaster. If your disk set is RAID 1 then you "merely" copy the data from teh surviving disk onto the new mirror. If you are using RAID 5, then the new disk must be buidl with "calculated" data. That is the data from all the other disks (whether it is real data or parity data) will be need to be read from the surviving disks. That total data is then used to calculate the data going on to the new drive. Now for a personal opinion. I will be building a server for my church. I plan on using ATA100 drives with (probably) the Promise RAID card. I will use RAID 1. Hope this helps. -pen
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