SAS or SATA

[ochadd]

Am I wrong in believing there is no benefit in going with SAS over SATA for the setup below?

I'm looking at upgrading a file server with a four drive RAID 10 set on a PERC 5/i controller. Leaning towards the Seagate ES.2 500GB drives. They come with the exact same specs outside of the interface but the SAS drive is $173 vs SATA for $90.

The differences I'm aware of between SAS and SATA is the queue depth and cable length. Sata allows 32 requests in the queue compared to 60k+ for SAS. The max I've seen in perfmon on the current three drive RAID 5 set is 24.

 

[Keitero]

If you don't do a lot on access and need the speed of SAS, stick with SATA. It's cheaper and you get much more space/buck.

 

[mooseracing]

SAS has full duplex bandwidth where as SATA does not, at least from some readings I have seen on the web.

Also let me know when you can get 600MB bursting with 2 drives on SATA.

Forgot to mention, doesn't Perc5 have a bandwidth of 300MB/s? That should play into you drive choice as well.

 

[Keitero]

No, but 425MB/s is close for SATA.

For the price and for most users, SATA is good enough. Those 5% or so (myself included) want that extra yard and are willing to pay the price for it. (Hence why I spent $600+ on a SAS card. :-/ )

 

[ochadd]

Originally posted by: Keitero
If you don't do a lot on access and need the speed of SAS, stick with SATA. It's cheaper and you get much more space/buck.

Also let me know when you can get 600MB bursting with 2 drives on SATA.

Access speed is definetly an issue. My understanding is that a SAS drive is not inherently faster than SATA. The Seagate ES.2 drives have exactly the same performance specs but the SATA version comes with 32mb of cache while the SAS comes with 16. Seems backwards eh. I don't see any reason one would by the SAS version compared to SATA unless SAS provides some inherent interface bonus that would improve on a four drive RAID set.

 

[VirtualLarry]

Is SAS better than SATA? In what way? What are the prices like on SAS drives? Can I multiplex multiple SAS drives onto one SAS connector?
My motherboard, MSI K9A2 Plat., has a promise TX3 SAS controller built-in. It has two SAS ports on the mobo.

 

[her209]

Originally posted by: mooseracing
Also let me know when you can get 600MB bursting with 2 drives on SATA.

Do SSD SATA drives count?

 

[Loreena]

Burst has little to do with real world performance so the numbers should be taken with a grain of salt. The only benefit to having it reported in the first place is to make sure you don't have a bus issue which was a big issue with VIA chipsets back in the Athlon days. Most of the programs (i.e. HD Tach) now don't even report burst speed correctly particularly on AHCI disks on ICH9 etc.

Where SAS shines is if lots of disks are needed in multiple configurations. It's a waste to go to the expense if you only need two disks. Unless you must have the access time of 15K disks AND their capacity.