Hard Drive Speed: Why Am I Not Getting 375 MB/s?

[rahulkhajuria]

I have 4 p.c.s with SeaGate Barracuda ST3250310AS 250 GB Hard Disks installed in them . These pc.s have 2.7GHz AMD Athalon 64 X2 CPUs & Asus M2N68-AM SE2 Mobos . There is 2 GB DDR2 RAM installed in each of these machines (not dual-channeled) . They also have XFX GeForce 8400GS Cards . However when I transferred a 1.54 GB Folder from 1 Partition to another in each of these machines , the folder was transferred @ 20 to 30 MB/s .

My other machine is a Pentium D 820 2.8 GHz with 512 MB DDR RAM & 80 GB Western Digital WDC WD800BD-22LRA0 (74 GB) Hard Disk . The mobo is MS-7101 fom MicroStar . Even on this machine , when I tried copying the file from 1 Partition to another , I got a speed of about 10 MB/s .

The connection protocol on all p.c.s seems to be ATA/ATAPI 7) .


My Question is as follows :

I recently found out from Wikipedia that Sata Hard Drives support 150 to 600 MB/s speed . Also , on the Seagate Website , the Barracuda ST3250310AS 250 GB Hard Disk is mentioned as having 3Gb/s speed (about 375 MB/s) . Then why am I not getting such speeds from my Hard Drives ?

 

[dE_logics]

When you copy files from within a hardrive, the needles have to move about the whole hardrive reducing speeds dramatically.

There speed measured is by transferring data to and from a ram disk. Usually it won't go below 85 MB/s.

Tips of life: Never buy a Seagate.

 

[rcgldr]

The high speeds you're mentioning are the interface speed of the SATA interface on the drives. The speed you're looking for is the streaming media speed, which is mostly a function of rpm (usually 7200 rpm) and capacity per platter.

I'm assuming you're transferring data from a partition on one hard drive to another partition on another hard drive. If you're transferring data from partition to partition on the same hard drive, then the transfer rate will be much slower due to all the drive head seek time when switching between partitions.

Seagate 7200.12 (500gb part number = ST3500418AS) SATA drives have 500gb per platter (250gb per surface) and a maximum media speed of 125 mega-bytes/second. The average speed will be more like 70 to 100MBPS. The new Barracuda XT is still 500gb per platter, but has a max of 138 mega-bytes per second.

Seagate was the first to have 500GB per platter (250GB per side), but that was over a year ago, and I assume that other brands are also at 500GB per platter now. I'm not aware of any drives exceeding 500gb per platter at 7200 rpm yet so the media speeds haven't changed much in the last 1 1/2 years or so. WD usually doesn't specify the number of heads on a drive, which would let you determine the capacity per platter, but they do include maximum transfer rates. The newest 2TB drive matches the Seagate 2TB XT drive at 138 MBPS. The 1TB version is speced at 126MBPS, lower capacities are spec'ed at slower still rates. I don't know about other brands.



If you need the transfer rate, you might consider pairing up hard drives for raid 0 (striped pair), although it won't double the transfer rate.