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Sata II..
- Thread starter Jason711
- Start date
SATA II was designed as a subset SAS(serial attached scsi). SAS devices can most definetly use the full 3 gb speed. SAS will be used as a link between drives and between an eclosure and a hba. The link between the hba and enclosure will most definetly use 3 gb.
Right now this no way you will even come close to using the full 3 gb speed.
Right now this no way you will even come close to using the full 3 gb speed.
Well, I don't think you could technically call SATA II a subset of SAS since they use completely different command sets.
Current SAS systems will happily talk to a 1.5Gb/s SATA drive, even for example, through a SAS expander (kind of a switch) where the host adapter will talk to the expander and SAS peripherals at 3.0Gb/s, but talk to SATA devices at 1.5Gb/s. So I guess it isn't really necessary for single SATA devices to have 3.0Gb/s connections as a single drive may never use that much (as of now... who knows what the drive manufacturers have up their sleeves!)
Current SAS systems will happily talk to a 1.5Gb/s SATA drive, even for example, through a SAS expander (kind of a switch) where the host adapter will talk to the expander and SAS peripherals at 3.0Gb/s, but talk to SATA devices at 1.5Gb/s. So I guess it isn't really necessary for single SATA devices to have 3.0Gb/s connections as a single drive may never use that much (as of now... who knows what the drive manufacturers have up their sleeves!)
Jason711 said:
Well, SATA I devices will work with a Port Multiplexer (expanders only exist in the SAS world, they're slightly different from a por multiplexer), but you will need a SATA II controller. The reason you need the newer controllers is the addition of a Port Multiplexer port selector field in the standard SATA FIS (command structure)
Hmm, well, let's see if I can do a better job of explaining it...Jason711 said:break that down retard style.
A port multiplexer is something that's used to connect multiple drives to a single SATA port.
In order for the port muliplexer to know which drive it is talking to, the SATA II specification has added a field in the SATA FIS (that is the structure that is used for commands sent to the drives, such as Read or Write, etc.) that tells the port multiplexer which drive to send the command to.
Since only the port multiplexer and controller have to be aware of this field, you will need a SATA II controller to use a port multiplexer, but you will be able to attach SATA I drives to the multiplexer.
Does that make more sense?
doormat said:
There may not be too many SATAII raid controllers because SAS can every thing SATAII can do plus more. Being that is fully back compatible with SATA drives. We will probably see more of these.
We just got a 6 port SAS raid card at work. So they aren't too far way for consumers. No idea on what the cost will be like.
Jason711 said:
Well, in effect. SATA will always remain a point-to-point connection (only one device/controller on each end of the cable).
A port multiplexer will have one SATA port that connects to the host controller and up to 15 ports that can connect to drives. Each drive will need its own cable.