SAS vs. SATA

[TeeJayHoward]

Just how interoperable are these two?

I've heard that you can stick a SATA drive on a SAS controller, but how close are the specs? Like, you know the SATA hot-swap enclosures? Can you stick a SAS drive in there? Can you use a SAS card to connect to the SATA enclosure?

*blinks*

Would it be possible to have a 5 bay SATA enclosure with 2 SAS drives and 3 SATA drives, if it's connected to a SAS controller card? Would it limit the drives to SATA speeds?

With the SAS controllers costing about the same as the SATA controller cards these days ($300 or so for an 8-port card) is there any reason to NOT buy one?

Oh, and does anyone have any links with more info on SAS? I'd appreciate it muchly.

 

[defakto]

You can put SATA on SAS but not SAS on SATA the SAS connector its self is designed to prevent this. So you could have a 5 bay SAS enclosure with 2 SAS and 3 SATA.

Speed is basically by port with an SAS controller, from my understanding. I haven't played around with one yet to know for sure. Several others on the forum have and could tell you more on that. SAS drives will most likely be higher performance and much higher cost than SATA as they are geared toward high end/ enterprise markets.

Another upside to SAS, and I think SATA 2, is the addition of port multipliers. One channel of SAS can actually have more than one drive on it, be it SATA or SAS.

Here's some technical pdf files on SAS standard

SAS
SAS1.1
SAS 2.0

 

[Lazn_Work]

You could put a SATA enclosure on a SAS controller, but you could only put SATA drives into it. (not SAS drives)

You could put a SAS enclosure on a SAS controller and put a mix of SATA and SAS drives in it.

You can not put a SAS enclosure on a SATA controller, nor SAS drives on a SATA controller.

==>Lazn

 

[TeeJayHoward]

All righty! Thanks, guys.

 

[DougLite]

Paging UlCompE02...

 

[UICompE02]

Paging UlCompE02...

Here I am!

Technically, SATA backplanes prevent the insertion of SAS drives...

However, if you're adept with a Dremel (or similar rotary tool), you can knock out the key and use a SATA backplane as a SAS/SATA backplane. I have done this before with some SuperMicro SATA backplanes and haven't had any problems. Most SAS controllers will use a 4 wide connector, so you'd have to get a cable that goes from a four wide to single connector to connect to the SATA ports on the enclosure. (we call these cables 'squids'). All of the SATA enclosures I've looked at (quite a few) have no problem running at 3.0gb/s, which is the fastest current SAS rate.

It actually may be possible to use a SAS enclosure on a SATA controller as well. What you need is to make sure you have the right type of connectors and cables to make that happen. The SAS specification has a 4 wide connector that the SATA spec does not use. Both, however, share the same single lane connector. This means you can get a SAS enclosure (if it doesn't use an expander, this will only work with direct-connected devices) with a 4 wide connector and use a 4 wide to single lane cable to connect to a SATA controller. In my experience, though, most SAS backplanes/enclosures will have an expander on them, so they will only work with a SAS controller in that case.

Another upside to SAS, and I think SATA 2, is the addition of port multipliers. One channel of SAS can actually have more than one drive on it, be it SATA or SAS.

SATA-2 devices allow the use of port multipliers. SAS includes what are called expanders. Expanders have much more intelligence than a port multiplier and support things such as wide ports and cascading.