![]() This allows you to create servers using storage in more than one chassis. ![]() Internal connectors can be transformed into external connectors using an adapter plate. This is a SFF8087-to-single-SAS breakout cable this is a SFF8643-to-single-SAS breakout cable.Īlso, in some scenarios, a mainboard may offer discrete SAS ports which you desire to aggregate into a multilane cable, and so reverse-breakout cables are available as well. For example, if you get an SAS HBA, it probably comes with one or two SFF8087's on it, but you may want to directly attach hard drives. Again, four lanes gives you 48Gbps over a single SFF8643 connector.Ī multilane connector may be broken into its four individual lanes using a breakout cable. Some newer boards are using SFF8643 ("Mini SAS HD") for SAS 6Gbps.įor SAS 12Gbps, this is the SFF8643 (internal, "Mini SAS HD") and SFF8644 (external) connector. Four lanes gives you a total capacity of 24Gbps over a single SFF8087 connector. However, most SAS deployments involve larger numbers of disks, and SAS has some special connectors used to reduce wiring and aggregate lanes together.įor SAS 6Gbps, this is often the SFF8087 (internal, "Mini SAS") or SFF8088 (external). It is therefore best to use cables less than 1 meter long if at all possible. The difference is that they can be longer. That absolutely won't work.Īs already noted, single SAS internal cables are virtually identical to SATA. You cannot connect SAS drives to a SATA port. 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 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 In particular a lot of it has 2TB size limitations. ![]() ![]() that doesn't 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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