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Windows 7: slow disk bandwidth with GA-Z77X-UD3H, Win 7 Ent

06 Nov 2014   #1

Windows 7 Enterprise SP1 64-bit
slow disk bandwidth with GA-Z77X-UD3H, Win 7 Ent


in a nutshell, i've got some fast drives that should be transferring data much faster than they actually are [30mbytes/sec], and i can't figure out why they're not performing right.

i've got 2 disk drives i'm going to be copying data back and forth from -- a seagate st3320620as 320gb sata drive rated at 72mbytes/sec sustained max throughput, and a western digital wd10ezrx sata3 rated at 150mbytes/sec sustained max throughput.

the mobo i'm using is a gigabyte GA-Z77X-UD3H, which has 2 x sata3 ports rated at 6gb/sec. i've connected my drives to these two sata3 ports.

i've set the bios to use ahci, and the bios system devices screen shows both disks recognized on the appropriate sata3 ports as distinct disks. my bios is flashed to the latest non-beta version [f18].

the drivers originally on the machine were from microsoft, device mgr tells me they're version 6.1.7600.16385 dated 6/21/2006, using atapi. i updated to use intel's rapid storage technology drivers [v., 8/2013] -- still no joy.

anybody have any ideas on how i can troubleshoot this and get the speed i'm supposed to get?


My System SpecsSystem Spec
07 Nov 2014   #2

Microsoft Community Contributor Award Recipient

Windows 7 64 Bit Home Premium SP1

The speed ratings given by hard drive manufacturers is a theoretical maximum. Rarely do we see real world speed even approach these ratings.

The transfer speed you actually get is dependent on a number of factors. If one of the drives is a SATA2 (3Gb/s) drive you will be limited to SATA2 speed regardless of the SATA controller speed or the second drive's speed.
It also depends on the direction the file is going - from SATA2 drive to SATA3 drive will be faster than the other way around because writes take longer than reads.
It also depends on the type of file and how fragmented it is. Large video files that are broken up into little chunks all over the platters will go much slower than small contiguous files.

If you run a test program like HDTune you can see what base speeds you can achieve on each drive on your system setup. Then compare those speeds to your actual transfer rate to see if you are in the ballpark.

It can get strange from time to time. I have often seen my transfer rate being much faster over an Ethernet connection than from disk to disk on the same system. Go figure!
My System SpecsSystem Spec
07 Nov 2014   #3

Windows 7 Enterprise SP1 64-bit

hey, thanks for the input, tv. yeah, one of the drives is sata-2, the other is sata-3. the sata-2 drive is rated at 72mbytes/sec, though -- a far cry from what i'm seeing, even when it's the one performing the reads while the other one writes. going the other way around is maybe a little slower, but the difference seems pretty negligeable.

what you've said about fragmentation makes a lot of sense, and what i've seen supports that. for example, some of the files i'm transferring -- big, contiguous ones -- go up to 50mb/s, an increase of 20mb/s over my de facto average. but even then, that's still only 2/3 of what the sata-2 drive should support. :?

i'm also transferring files to/from another disk, a 10,000rpm sata-3 drive, and even here i'm not seeing throughput even close to what's advertised. both of the drives are supposed to support 150mbytes/s, but even when both are connected to the mobo's 6gb/s sata-3 ports, i'm getting only about half that.

what is this hdtune program you speak of ? is this it ?

also, do you think i'm dealing with some inherent hardware limitation[s] here, rather than a windows-7 driver/config issue ?
My System SpecsSystem Spec

07 Nov 2014   #4

Microsoft Community Contributor Award Recipient

Windows 7 64 Bit Home Premium SP1

Well, 50 is pretty durned good in the real world. I rarely get faster than that.

Yes, that is the hdtune benchmark program.

I believe you are dealing with the hardware limitations of your total system and the type of files you are dealing with.
You can't believe everything you see in marketing. SATA3 drives are faster than SATA2. But your mileage will (always) vary!
My System SpecsSystem Spec
09 Nov 2014   #5

Windows 7 Enterprise SP1 64-bit

heh... yeah, now that you mention it, i guess spec sheets -are- basically marketing. thanks much for your help !
My System SpecsSystem Spec

 slow disk bandwidth with GA-Z77X-UD3H, Win 7 Ent

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