Newbie needs help on RAID

J

johannes_

Registered
Hi everybody!

I know next to nothing about RAID, except what RAID 0, 1 and 5 are. Now we want to set up a file server for our office. Here is what we need:

- Only 3 users
- Huge disk space (>500 GB, more in the future)
- Cheap (with cheap being the limiting factor here)

I thought of using a Mac mini and several Firewire disks to set up either a RAID 1 or RAID 5. I don't want a hardware failure to knock out our file server. Using a Mac mini, I would also use the client version of Mac OS X, not Mac OS X Server.

1. Is this idea good? Stupid? OK but better solutions exist?

2. Would Apple's software RAID work here? Or is it so unbearable that you'd recommend something else?

3. If I had a RAID 5, can I expand it just by adding another disk? How can I expand a RAID disk without having several volumes mounted on the desktop of the server?

4. Are there any tutorials or FAQs on RAID and the Mac? As you see I know next to nothing. :-(

By the way I don't care for speed. We will work on local copies most of the time and only commit the changes to the file server once a day or so (probably using Subversion).

Thanks for your help!
 
I would recommend against using FireWire drives in a RAID fashion -- for one, you're going to have to "daisy-chain" the drives together since there's only one FireWire port on the mini, and this can cause latency issues in some scenarios.

Your best bet would be to simply hook the drives together and share them as individual drives.

RAID would be useful if you were in dire need of speed, and only then with internal PATA or SATA drives... external SATA drives would also work, but not with the Mac mini.

To increase or decrease the size of a RAID array, you would have to rebuild the array (a software procedure) every time you added or removed a drive.

It would be more headache than it's worth on the Mac mini, in my opinion.
 
Thank you for your help!

Speed is not so important. Important is the size of the volume and that it is stored on redundant disks. I had a disk die on me before and I don't like that. (I will host Subversion on the server and need the big volume for the repository.)

Rebuilding the array, can I loose data there? I mean apart from sudden power outages etc. Do I have to copy everything to another disk and then back?

You say it is too much headache with a Mac mini. Would you do it with another Mac? Apart from the XServe, it is outside our budget. Or would you use Linux and a cheap PC? But I don't know anything about Linux, I'd prefer a Mac.
 
I would then opt for some good-sized external FireWire enclosures that allow chaining (they'll have more than one FireWire port on the back).

I would go with a nice RAID setup if I had a tower machine -- not a Mac mini. With a tower, you can add a hardware RAID PCI card which would be much faster than Apple's software implementation. It would also be cheaper, since you only need bare drives... not drives AND enclosures, not to mention internal drives don't use up valuable power sockets!

I do believe you can increase (and possibly decrese) the size of a RAID set, using the "grow" command -- whether that's supported on Mac OS X is something I don't know. I would suggest building the RAID with a capacity that won't change for a while, so you can get familiar with everyday use first before moving on to more advanced rebuilding/growing/shrinking stuff.

If you've got an older G4 tower, they make great servers. Pop in another cheap ethernet card, and you can have a proxy/firewall/DHCP server as well. While that stuff will be infinitely easier with the Server flavor of Mac OS X, it's still possible with a client version of Mac OS X -- you'll just have to dive into the terminal and follow some walkthroughs, easily found with Google. There may even be some utilities on versiontracker.com that will help configure such services graphically.

All in all, the Mac mini may make a decent medium-load server. Attach a few, large, non-RAID FireWire drives to it, download "SharePoints" from versiontracker.com, and you're ready to go for simple file sharing.

Here's some nice, easy RAID information:

http://www.acnc.com/raid.html
 
WiebeTech (http://www.wiebetech.com/home.php) offers some cheap little RAIDs in little enclosures which may suit you well and they hook up via FireWire or USB. I assume a XServe RAID is out of the question.

Hardware malfunction will destory a RAID no matter how you look at it. Hard backup is the only solution (AIT or mirroring). Mirror is good (redundant) but write performance is poor and you lose 1/2 the overall capacity. Level 0 is bad unless you backup but I/O is good. Level 5 is good with a hot swap but you should still backup. Heck, you should always backup.

Basically, you can never trust a disk, they're likely to break and a RAID is comprised of many of the little suckers. Do the math. :)
 
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