SATAII 3Gb/sec vs 6Gb/sec

[walter.sk]

I'm running a Win7 64-bit machine that came with an internal SATA II drive rated at 3Gb/sec.  I bought a second internal drive for data that was SATA II rated at 6Gb/sec.  It seems compatible with my machine, but does the higher 6Gb/sec rate give me any advantage over having got one at 3Gb/sec?

The CPU is an i7-930, and all of the drive options offered (by Dell) are the SATA II 3Gb/sec type.

[Steve Weldon]

Without knowing the exact drive or it's specifications it's impossible to say.

If the drive is capable of saturating (exceeding) the SATA II interface (anything over 300mbps transfer speeds) then yes, a SATA III (600mbps max) can make whatever difference there is over 300mbps.

For instance, I'm fond of the Crucial C300 256gb SSD's which are SATA III compatible.  I run one in a SATA II Thinkpad and it tops out at about 260mbps read and 198mbps write, and on a SATA III enabled workstation the same drive achieves 361mbps read and 201mbps write.

So it appears the extra bandwidth of the SATA III interface can make more difference than you might first think.. but only if the drives capabilities exceed that of SATA II.

[walter.sk]

Thanks for the information.  My computer has an SATA II controller, and the first drive is a Western Digital Caviar Black WD2001FASS 2TB drive.  The second drive is a WD2002FAEX 2TB drive rated at 6Gb/s, while the first is 3GB/s.  Apparently it can determine that the controller is SATA II, and set itself accordingly.

I suppose I should get the faster drives in case I ever decide to upgrade the controller.

[Steve Weldon]

Those are WD's latest drives.  With the cache they can do bursts up to roughly 200mbps in the right circumstances, but any extended transfer almost immediately drops down to 70-80mbps. 

My guess is at this point its mostly a marketing tool, though with Sandy Bridge at our doorstep SATA III and USB3 are now becoming the standard interfaces like USB1 yielded to USB2.. and to this day there are plenty of USB1 (transfer speed capable) devices still on the market.  Some types of devices are limited by their design more than their interface, and at the moment mechanical hard drives are one of those devices.

Though... and it seems like there's always an exception..   I was recently reading a review about an interesting device that 'holds' a 3.5 inch mechanical hard drive AND a 2.5 inch SSD, and then fits in a standard 3.5 inch cage.  The idea is to use the SSD as a sort of extended cache.  The controller isn't a smart real time controller like on the Seagate's interesting hybrid drives, but rather it takes stock of the most used files on each reboot which seems to work with a larger SSD vs. the 4gb small SSD cache of the hybrids.  Something like this, if paired with a SATA III speed SSD (I know of only one, the Crucial C300 I linked above) could benefit from a SATA III interface.

Anyway.. my point is hybrid devices with fast burst speeds might eventually saturate SATA II but we're a ways off from that.

[bradleygibson]

SATA II devices will work just fine on a SATA III controller without issues.  (No need for any special drivers, etc.)

Most SATA III devices will work on a SATA II controller (but you might have to set a jumper on the device--be sure to check the docs).

Note that mechanical hard disk drives are too slow to saturate a SATA II bus, so plugging the device into a SATA III port will have no effect on performance.  You can ignore burst numbers, as these figures are quoted from the devices memory (typically 8MB)--unless your files tend to be really really small (and you don't need them all that often (and they happen to be laid out in the order you need them on your hard disk (you get the idea))) this figure won't help you.

Steve's quite right that some SSD's are capable of sustained transfers (not burst transfers) in excess of 300MB/s, in which case you would want to ensure the device is SATA III and your motherboard is SATA III.  Note if you're using RAID'ed SSD's on Windows7 or SSD's at all on Macs or Windows XP/Vista, you need to pick the right drives in order to avoid seeing a performance degradation (see http://en.wikipedia.org/wiki/TRIM for more on that).

HTH,

[walter.sk]

Thanks, Bradley and Steve.  Stuff is getting too complicated for me at my level of understanding, so I will just get more of the same drives I have for data use and backup of same.

[bradleygibson]

Ok, sorry if I made it sound complicated--it's hard to know how much info people are looking for, so, when I can, I usually try to provide more complete answers.  Hopefully to avoid someone going out and buying something, then being surprised.

The short answer to your question is your new internal drive, if it's 6Gb/s, is a SATA III drive, not SATA II.

Regardless, it'll work, and your system will *not* slow down that drive, despite it's higher rated speed.  That rating will offer no real-world advantage with that drive.

HTH,
-Brad

[Steve Weldon]

"Regardless, it'll work, and your system will *not* slow down that drive, despite it's higher rated speed.  That rating will offer no real-world advantage with that drive"

Absolutely correct.  And to be very clear, your interface is rated at 6gbps, but your actual drive is still operating way below the speed of SATA II's maximum threshold.

Purely a marketing gimmick at this stage.. you can't even say it's a 'future proof' drive for SATA III only machines unless some genius fails to make them backwards compatible..

[walter.sk]

Thanks, guys.