Storage rant #1

I've been doing sysadmin for awhile now. I've seen disk space go from > $4 per megabyte(!) to less then $240 for a terabyte. Space requirements have gone up too. You used to be able to have your compiler, editor and source on a floppy.

My general rule has been local disk for databases and other things that need locking, NAS for everything else. The local store can be a SAN of course. Centralize storage as much as possible (but no more so) to keep backups from going over the network. Because it's centralized, you can do RAID to increase reliability.

Backups are not archives! Backups are so you can recover your setup as close as possible to the latest good state if the hardware fails completly. If you want to go back to a point in time, that's an archive.

Backups have changed dramatically over the years. I don't think there's such a thing as an inexpensive tape anymore. At least something that's dramatically cheaper then disk. I once bought a 2GB 4mm DAT to backup my home systems. I probably had 1GB at the time. Now you're going to need multiple tapes to span your disks. Because of that, you probably also want an automatic tape system as well.

After you figure out your backup cycle (how far back a backup goes (archives are forever)) and how much data you have, you arrive at the total data storage. If you go tape, figure out the automated drive cost with a full compliment of tapes. You might find that is cheaper to buy a disk farm of some sort for your backup store. Remember, backups are not archives.

You'll still probably want to put data offsite. But the disks do have the advantage of matching the speed of incoming data. Your backups will always be much quicker to disk then tape so your window will be larger. When you create media for offsite, it'll be done on the disk farm so it will go quicker.