What would be faster? 4 SATA SSDs on 2 SAS ports or 4 SATA SSDs on 1 SAS port?

Freek

It might be a rhetorical question I am asking here, but I am building a rig with 4 Crucial M4 256GB SATA SSDs that will be connected to a RocketRaid 2720 which has 2 SAS ports. I bought 2 '4xSATA to SAS' cables and was wondering what would be faster: All those 4 SATA SSDs connected to 1 SAS port, or divide them between the 2 SAS ports, so 2 SSDs for each port? I assume to divide them would be faster, or am I wrong? The setup will run a RAID10 configuration. Thanks

PAD

I would assume that 2/port would be faster, but I'm not too sure. Pretty sure someone will step in and give you some good advice soon.

djvdorp

I think higher speeds could go over 2 ports at a time then 1 at a time.

gsrdgrdghd

As this is a very specific situation i don't think many people have experience with it. So i'd suggest you just set up a test system and do some benchmarking

pcan

The speed will be the same on both arrangements. The mini SAS SFF-8088 connector has individual data lanes for each of the four SAS ports. The 4xsata to SAS cable has no expander function: it does only a mechanical split of the data lanes.

Freek

Thanks for the replies guys!

Sadly I'm on a tight schedule so I don't have too much time for benchmarks.

@pcan Thanks! However, the box says (and this may sound stupid) 'SAS/SATA 6Gbps PER PORT'. So wouldn't that split 6Gbps / 4 in one occasion and 6Gbps / 2 in the other situation, making the latter more faster?

pcan

Your controller, like most modern SAS controllers, has 8 independent 6Gb SAS ports: 4 SAS ports for each mini-SAS connector. To reduce the number of cables in rack servers with hot-swap disks, 4 independent connections are consolidated in a single mini-SAS connector (type SFF-8088 or SFF8087). This way, on the rack server you will see only 2 cables connecting the controller to the SAS backplane. You are using a non hot-swap enclosoure, so you need cables with 4 individual SATA connectors at one end, and a single mini-SAS connector at other end, but each SATA cable is connected to an individual SAS port. I suggest to use both cables for redundancy purposes. Put a label on each cable, to avoid connecting them to the wrong connector during server maintenance.

Freek

@pcan Awesome, thanks for the explanation! I totally understand now :) Kudos +1 (Already labeled them :) )

jarland

Is that hasselhoff? Derail post #1

Freek

jarland

I like you.

djvdorp

I wonder about your age @Freek ;p

Freek

@djvdorp My current age is the legal drinking age in Las Vegas... (Google it ;) )

djvdorp

@Freek said: @djvdorp My current age is the legal drinking age in Las Vegas... (Google it ;) )

21? so am I :P

Freek

If that's what the legal drinking age is in Las Vegas, then yes ;) Else if, no :P