Conclusion
After lining up many new SAS hard drives, three representative controller solutions and two storage appliances, it is obvious that it was entirely worth waiting for SAS. If you read the technical documentation about SAS, you'll understand why. Not only has the serialized version of SCSI been transformed into a fast, convenient and easy-to-use storage interface, but it has also reached a level of scalability and sophistication that makes Ultra320 SCSI look like a stone age leftover.
Besides, interoperability is very smooth. If you were toying with the idea of buying professional SATA equipment for your server(s), you really should really think about SAS instead. Any SAS controller and enclosure available is compatible with either SAS or SATA hard drives and is thus suitable for either high-capacity SATA or high-performance SAS environments - or both at the same time.
Externally-operated storage devices are the next advantage for SAS: While SATA hardware either used proprietary cabling or is based on a single SATA/eSATA link, SAS links scale up in units of four SAS connections. This allows for matching bandwidth to the actual requirements rather then being stuck at UltraSCSI's 320 MB/s or SATA's 300 MB/s. Moreover, SAS expanders can be used to cascade SAS devices, giving administrators a powerful operating range.
Any future performance benefits will also only be available for SAS devices. We expect the industry to reduce its UltraSCSI offers to a level at which it does no more than support existing UltraSCSI deployments. All new hard drives and the latest enclosures and appliances, as well as interface speed upgrades to 600 and eventually 1,200 MB/s, are geared for SAS.
So, what storage infrastructure should you buy today? With the availability of SAS, the days of UltraSCSI are numbered. The serialized version does everything better, so whether to get UltraSCSI or SAS becomes obvious. The decision becomes more difficult if you choosing between SAS or SATA.However, as long as your storage requirements are clearly assessable on the long term, SAS components likely offer the better bang for the buck, which is certainly the case for high capacity near-line storage scenarios. Indeed, for maximum performance or big time scalability, there is no alternative to SAS.
