Apple’s staff gets a little testy when challenged regarding the company’s reliance on parallel ATA (or just plain ATA) for its Xserve servers and Xserve RAID storage arrays. ATA is unquestionably long in the tooth, but it’s important to understand that newer Serial ATA (SATA) drives don’t represent a new class of disk drive, just a different flavor of controller interface.SATA is a godsend for desktop and deskside systems where ATA’s 40-pin IDC box connectors suck up a lot of valuable motherboard space, and broad 40/80-conductor ribbon cables stuff up cooling airflow and make system maintenance more difficult. ATA cables are also notorious for shaking loose and, in systems that are opened often, developing bad conductors from too-frequent bending.However, in a server or array with a hot-plug, removable drive backplane, ATA is just dandy. There, the internal box connectors and ribbon cables are fixed in place. Links between the controllers and the removable drives are made using connectors comparable in quality to the 80-pin Single Connector Attachment (SCA) standard used in SCSI backplanes. The inconvenience of parallel ATA’s cabling doesn’t enter the picture with Xserve RAID, nor does the fragility of cables and connectors used in desktop systems. Parallel ATA has powerful cost/performance advantages when used in servers and arrays. ATA controller chips are highly integrated, so much so that a small controller board can be stuffed with several independent ATA controller chips, or custom chips containing multiple ATA controllers, with each controller dedicated to communicating with just one or two drives. Because of this, ATA-based arrays scale extremely well despite their low cost. One Xserve RAID array easily saturates its dual 2 gigabit Fibre Channel ports.I say this as a reformed SCSI snob. My reformation was set in motion long before Xserve RAID. Almost ten years ago, I had a chance to test a prototype controller-per-drive ATA array and was astonished by its continuous data transfer rate. It skunked my prized SCSI array by a good margin especially when operating at RAID level 5, in which parity data is striped across all drives in the array.If you engineer a storage solution properly, it doesn’t matter what it looks like under the hood. You can poke around inside Xserve RAID if it satisfies your curiousity, but arguments against Apple’s use of ATA are made moot by its performance. To my mind, if an internal architecture has the potential to continuously saturate the external bus, it passes muster. So while I ask Apple about ATA in my role as a proxy for my readers, the ATA question isn’t a question to me. Software Development