Lately I've gotten a flurry of questions about the suitability of Serial ATA (SATA) drives for use in entry-level and midrange servers. Obviously, the easy answer is "yes, they work great and are an inexpensive alternative to SCSI." However, the more accurate answer isn't quite that simple.
The biggest problem I've seen with the use of SATA drives is that vendors or buyers of those devices tend to stick a couple of large drives in the computer and assume that capacity will fulfill disk requirements, especially in entry-level systems. Large-capacity (i.e., up to 400GB) SATA drives are so inexpensive that it seems to make sense to throw in the biggest drives you can afford. OEMs encourage this practice, offering their entry-level systems with a 120GB or 250GB drive as available configurations.
The problem is that, from a best-practices perspective, you shouldn't be sticking your OS and all your data on one drive. Too many things can go wrong with the OS--from simple crashes to nasty virus infections--to risk housing your data and OS on the same drive. Even when vendors try to address this concern, their solution isn't always optimal. For instance, one major server vendor recommends that its entry-level servers be equipped with at least two drives, which, on the surface, seems like a good idea. However, the vendor is actually recommending two drives so that they can be mirrored. Mirroring provides additional insurance against disk crashes but still leaves you open to virus infections and malicious software (malware) attacks.
If you have two SATA drives, I suggest that instead of mirroring them, you use the smaller one as a boot drive, configure the OS on it, and dedicate the second drive to data storage. If the server supports RAID (as do many servers, even entry-level machines), decide what type of RAID protection is suitable for the data drives. For the boot drive, which will change very little, choose a good backup and restore product that will ensure minimal downtime should you need to replace that drive. Or, if a virus infection or an OS failure occurs, you can use the backup to restore the OS to an operational state on the remaining functional drive.
SATA drives are a great boon to entry-level servers, and not because of their capacity or performance. (The new Seagate 400GB SATA drive is also available with an ATA 100 interface and effectively delivers the same performance over both interfaces.) The simplified cabling and increased cable lengths of SATA as compared with ATA mean that low-cost servers can have storage capacities once reserved for high-end boxes; it's now easy to deliver a server with more than a terabyte of SATA storage.
It's still important to remember that SATA isn't a replacement for SCSI in heavily utilized, high-performance environments. Although SATA offers improvements over ATA, SCSI's strengths still set it apart from SATA. If your primary need is to store large amounts of lightly used data, SATA is an excellent choice. For mail or database server applications, though, you're still better served--even at the entry level--by SCSI storage.