RAID Questions.
 

I currently have a Debian Lenny Server. I just bought a external 1.5TB HD to create rolling weekly backups.

Since I have everything backed up, I think I want to setup a RAID array with my current setup. I have a few questions.

My hard disks as of now are:
1x Quantum Big Foot PATA 6Gb (OS Drive :P)
1x Maxtor PATA 300Gb
2x Western Digital SATA 500Gb

Questions:
1. What is a JBOD: Just a bunch of disks? Will this allow me to setup multiple different hard drives as one contiguous space?

2. Can I have one dedicated OS Hard drive, then the rest of my drives on an RAID Array?

3. Can I have different drive types on a single RAID? PATA and SATA mix?

4. Setting up a JBOD, will this create more stress when trying to setup a backup then just using the drives separately?

5. Is it even worth my time when setting up a RAID or should I just keep my drives separate?

1) JBOD is nothing special, it's just more than 1 disk in no RAID configuration. It does not 'allow' you to set up these drives contiguously, linux allows this inherently.

2) Yes.

3) Yes, using a software RAID you can. Not all hardware RAIDs allow this.

4) No. AFAIK there is no 'setting up' a JBOD, you just install the drives.

5) If you have no specific reason to do so, then setting up a RAID is wasted time and effort, IMHO (unless you do it for the learning experience, then it's always worth it :D)

What I really want is to combine all my storage drives as one. I want all three of my storage drives to act as one large hard drive. Is there technology out there that exist into doing so? Am I on the right path? What should I start looking into?

Yes, you can do that. It's call LVM (Logical Volume Manager). You can set up a group, then add 'members' (whole disks, partitions, whatever), into it. The entire group is mounted/presented as one. So, to simplify, if you have three 250GB disks in one LVM group, you'll see one 750GB drive.

Be warned, though...if ONE member of the group fails it could take down the whole group. This depends on how you set it up, RAID level, etc., but software RAID can be complex. As a rule, hardware RAID is much better (in my opinion), and usually faster since you don't have the software abstraction layer for disk IO.

Awesome. I've been doing a little bit of reading on it. It looks like have to format and partition each drive to setup a LVM. Will this work if I have these drives setup independently, out of a RAID array?

What do you want RAID to accomplish for you? More reliability than non RAID? More performance than non RAID? Just more apparently contiguous space?

Right.

In the unlikely case that you have some hardware RAID support, JBOD means it is turned off. Most likely, you have "fake RAID" support in your BIOS and JBOD means that is turned off, which is almost always the way you should want it.

Linux software RAID is a lot more flexible than hardware or fake RAID at using a collection of dissimilar drives. But maybe not flexible enough to do much with your specific dissimilar collection of drives.

For flexible combination of space (not looking for reliability or performance benefits of RAID, LVM is more flexible than software RAID).

Do you have that choice to make (JBOD vs. separate)? In my experience JBOD means just using the drives separately and is offered by BIOSes that don't offer another way of just using the drives separately.

What are you trying to accomplish?

I personally prefer keeping drives independent, so I can reconfigure systems more easily when hardware breaks and/or needs change. So I don't use LVM and I limit my use of RAID.

If drive boundaries were not an issue, how would you partition the total storage available to you?

If you need to consider drive boundaries, what would that do to the way you partition?

You could setup RAID, but there are some consequences. I suggest use software RAID level 5. Create a 300 GB partition on each of the 500 GB hard drive and then include 300 GB hard drive as the third drive. For the last 200 GB of space on each of the 500 GB hard drive, you can do what ever you want. Though a software RAID-5 requires more processing power, so I suggest using at least a dual processor setup. As with all RAID setups, fixing them when the server is messed up is going to take a lot of work, so back ups are definitely a must with RAID compared to single disk setups.

In your case, you have a single disk setup and you are doing back ups, so you do not need RAID. If you want a fail-safe, I suggest get more of equal capacity hard drives and then put the journal on them, so you gain some performance and you include a fail-safe that is transparent when a server messes up.

I am going to do a LVM with all three of my hard drives. I do not have a GUI installed. How would I go about setting them up through the shell? Do I need to add them to the fstab? (That's a dumb question.)

What would happen if I mounted all three drives to one folder?