![]() The primary takeaway: You can connect SATA drives to an SAS port and it is expected to work. They're crummy, just another thing to break. Some people use a special device called an interposer to take an inexpensive SATA drive and make it look like a nearline SAS drive (usually to get multipathing). The secondary port may be supported by a backplane or enclosure to allow the attachment of a second host, or to allow multiple paths back to a host for a high-availability configuration. One is the primary and one is the secondary. This means that, electrically, there are two ports on the single SAS connector. ![]() SAS devices, however, are usually dual-ported. SATA drives are inherently single-ported, meaning that they can only be attached to one thing at a time. When a SATA drive is attached to a SAS port, it is operated in a special mode using the Serial ATA Tunneling Protocol (STP). The gap is there to block a SAS drive from being connected to typical SATA cabling, or to a SATA backplane socket. SAS drives are incompatible with SATA ports, however, and a SATA connector will not attach to an SAS drive. Physically, the SAS backplane connector has an area that will allow either the gapless SAS or the gapped SATA connector to fit. Electrically, the SAS port is designed to allow attachment of a SATA drive, and will automatically run at SATA-appropriate voltages. SATA drives can be attached to a SAS port. There are pictures of the top and the bottom of the drive connector. This second set of pins is the second (redundant) SAS port. The SAS drive connector does not have a gap, and instead has a second set of pins on top. ![]() The SATA drive connector has a gap between the signal and power sections, which allows separate power and data cables to be easily connected. SAS and SATA use different connectors on the drive. SAS normally operates at a higher differential voltage than SATA and can run over longer cabling. SAS and SATA operate at the same link speeds and use similar cabling. Similarities, Differences, Interoperability Most SAS 3Gbps hard drives are fine though. ![]() In particular a lot of it has 2TB size limitations. that do not support 6Gbps because some of it has "gotchas" in it. You probably want to avoid older controllers, cabling, expanders, etc. SATA and Serial Attached SCSI (SAS) evolved from those, using a serial bus and hub-and-spoke design.Įarly SATA/150 and SATA/300 were a bit rough and had some issues, as did SAS 3Gbps. Both were parallel bus multiple drop topologies and this kind of sucked. With the introduction of SAS 12Gbps, seems like "it's time" to do a braindump on SAS.īy the late '90's, SCSI and PATA were the dominant technologies to attach disks. ![]()
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