Originally posted by: jondercik
trust me for the cheap price of a RAID card and an extra drive its well worth it to have the extra assurance. What is an extra couple hundred bucks in the long run in a business environment.
RAID != backups. All RAID does it keep the system up and running when a single hard drive fails. It does not protect you from:
Bad hardware corrupting your data
Bad software corrupting your data
A virus corrupting your data
A user accidentally deleting their data
Two hard drive failures (unless you use RAID6 or multiway RAID1/1+0)
Physical destruction of the server (fire/flood/lightning hit/etc.)
You need a regular backup plan as well. RAID is not strictly necessary unless you need 100% uptime on the server, or you cannot tolerate losing data that was stored since the last backup (using, say, nightly incremental backups and a monthly full archive copy). For smaller amounts of data, you can backup to an external hard drive or DVDs; for bigger sets, you'll probably want to look at a tape loader, or even having a second server that you use to back up the first one (although here you'd still want some sort of occasional offsite full backup, in case the building burns down or the like).
If they're serious about data protection (using multiple daily snapshots, etc.) and want very high performance and expandability, you might want to look at low-end enterprise NAS solutions (like stuff from NetApp/HDS/EMC), but I don't know what your budget is. "Real" NAS solutions start in the tens of thousands of dollars; you can buy a fileserver for well under a grand (plus the cost of drives); you can build one for even less.
A fast CPU will help if you are serving lots and lots of users (especially for applications like Exchange), or if you are using software RAID5. Gigabit Ethernet-speed transfers can also put a pretty heavy load on the CPU, even with a good NIC with hardware acceleration (TOE). However, for a fileserver not servicing more than a few dozen users, and on a 100Mbps network, you can get by with a pretty low-end CPU setup.
Lots of RAM will help because it will give you a bigger filesystem cache (so very frequently-accessed files will be in RAM rather than having to be fetched from disk every time). You may also need RAM for server-side apps (unless this is *only* a fileserver).
For fairly sizable files, a striped RAID array (RAID0, 0+1, 5/6) will improve STR and make file reads/writes faster compared to single disks. They're also often better at queueing multiple I/Os simultaneously than a single drive. And a redundant array (RAID1, 0+1, 5/6) will stay up through a single drive failure.