Last week, we initiated our coverage of serial ATA, or SATA. Today we'll discuss several of the implications for enterprise storage in a question and answer format.Question:\u00a0 Does SATA belong in a RAID box?The answer depends on your expectations for such an array.\u00a0 Some aspects of SATA drives will not be as manageable as their Fibre Channel or SCSI counterparts. However, if your requirements don't include a need to twiddle some relatively esoteric dials for optimization and are mostly directed at getting highly reliable storage at a cheaper price, SATA may work just fine.Organizations that may find such devices to be suitable include companies that can't afford larger and more sophisticated arrays, remote departments, and enterprises whose data management is sophisticated enough to determine which files belong on high availability machines and which can be offloaded to cheaper devices.Question: What about the drive's internal makeup?\u00a0Reliability is a key issue with any storage device.\u00a0 ATA drives have historically had a lower mean time between failure (MTBF) than SCSI or Fibre Channel drives, but that has nothing to do with the ATA connectivity. Rather, it is a function of the market positioning of the drives.\u00a0 EIDE is very much a commoditized segment of the storage market.In order to reach lower price points the drive vendors squeezed as much cost out of their\u00a0hard disk drives\u00a0as possible and cheaper parts typically mean earlier failure.\u00a0 Thus, two 32G-byte drives from the same manufacturer might have near-identical performance characteristics but the more cheaply built disk behind the EIDE interface would be more likely have a component fail than would the more robust SCSI device.Question:\u00a0 Can we expect hot-plugability?The SATA specification supports hot plugging; so this issue will have more to do with the way the array vendors implement the connection.\u00a0 There is nothing to prevent the use of "hot spares" or swapping out drives on the fly.\u00a0 As is the case with hot swapping however, connectivity between drive and array will be through a "mid-plane" rather than through a cable to facilitate non-disruptive removal and insertion of drives.Question:\u00a0 What about the MTBF problem?Fortunately, you have a choice here.\u00a0 The 10K-byte drives will likely have components, performance and MTBF that is identical to what SCSI offers, but with capacity that is only a half to a quarter that of SCSI and Fibre Channel HDDs (so far, the Western Digital 36G-byte drive is the only 10K rpm drive I know of).Much larger but slower (7200 rpm) drives with a shorter MTBF will be available from Maxtor.\u00a0 Both are likely to make good sense in arrays, but you will have to decide if your choice is to be driven exclusively by purchase price or if performance is part of the decision.\u00a0 In either case, arrays using such devices are likely to be significantly cheaper than either SCSI or Fibre Channel.Question:\u00a0 What will happen to the prices?Expect prices for slower SATA drives to curve downwards as more Intel-based motherboards are built with the SATA chipset.\u00a0 Intel has embraced the standard and it is likely to start shipping boards with native SATA support this year. So it is only a matter of time that the low-end devices will begin to achieve the benefits of high production levels and higher yields for the chipsets they rely on.\u00a0 Faster devices will likely become cheaper as well, but at a much slower rate.Question: If they build them, will you come?This really asks at what price or price-performance point does a SATA array get interesting? My crystal fishbowl offers the following insight: it seems pretty clear that if the SATA array vendors can come in at a price at least 30% lower per gigabyte than SCSI for the higher performance arrays (the ones with the 10K disks), they have a definite play.\u00a0 Arrays with slower spin speeds will have to come in even lower, of course.\u00a0 You will have to do an ROI analysis to understand which, if any, is best for you.Question:\u00a0 What about Fibre Channel and SCSI?Today, Fibre Channel and SCSI own almost all the server disk market, with roughly five times as much SCSI storage sold as Fibre Channel storage.\u00a0 The SCSI players should be nervous about SATA pushing up into their sweet spot in the market, and they are.\u00a0 Their response has been to form a collaborative agreement for enabling Serial Attached SCSI system-level compatibility with SATA hard disk drives, although the results of this effort are surely a few years off.The physical compatibility between Serial Attached SCSI and SATA will have all sorts of implications for IT cost efficiency in the future.\u00a0 Imagine being able to mix-and-match your disks according to the way your business will be using them.\u00a0 In the mean time, the response of the SCSI community sure seems like a pretty good validation of what the ATA vendors are doing.