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Old 04-13-2005, 04:41 PM   #1
Registered: Apr 2004
Distribution: Gentoo
Posts: 65

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Hard drive access speed

I have a 200gb hard drive that's supposed to transfer at 100 mb/s but it's only getting around 50mb/s. I can't figure out what's wrong with it, unless it's just a normal thing for it not to get close to its 'maximum' speed. It's running udma5, it shouldnt be a cpu problem (2.0 ghz athlon), im using a 80 wire IDE cable, and it's set as Master. It has a shuttle AK38N motherboard ("IDE interface: VIA Technologies, Inc. VT82C586A/B/VT82C686/A/B/VT823x/A/C PIPC Bus Master IDE (rev 06)") that supports transfer speed at 133 mb/s. Here's some info from hdparm.

$ hdparm -tT /dev/hdc
Timing cached reads: 1216 MB in 2.00 seconds = 607.49 MB/sec
Timing buffered disk reads: 146 MB in 3.02 seconds = 48.32 MB/sec
$ hdparm -i /dev/hdc

Model=WDC WD2000JB-00FUA0, FwRev=15.05R15, SerialNo=WD-WMAEP2754094
Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
RawCHS=16383/16/63, TrkSize=57600, SectSize=600, ECCbytes=74
BuffType=DualPortCache, BuffSize=8192kB, MaxMultSect=16, MultSect=16
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=268435455
IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio1 pio2 pio3 pio4
DMA modes: mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5
AdvancedPM=no WriteCache=enabled
Drive conforms to: device does not report version:

* signifies the current active mode
$ hdparm -I /dev/hdc
ATA device, with non-removable media
Model Number: WDC WD2000JB-00FUA0
Serial Number: WD-WMAEP2754094
Firmware Revision: 15.05R15
Supported: 6 5 4 3
Likely used: 6
Logical max current
cylinders 16383 65535
heads 16 1
sectors/track 63 63
CHS current addressable sectors: 4128705
LBA user addressable sectors: 268435455
LBA48 user addressable sectors: 390721968
device size with M = 1024*1024: 190782 MBytes
device size with M = 1000*1000: 200049 MBytes (200 GB)
LBA, IORDY(can be disabled)
bytes avail on r/w long: 74 Queue depth: 1
Standby timer values: spec'd by Standard, with device specific minimum
R/W multiple sector transfer: Max = 16 Current = 16
Recommended acoustic management value: 128, current value: 254
DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5
Cycle time: min=120ns recommended=120ns
PIO: pio0 pio1 pio2 pio3 pio4
Cycle time: no flow control=120ns IORDY flow control=120ns
Enabled Supported:
* Host Protected Area feature set
* Look-ahead
* Write cache
* Power Management feature set
Security Mode feature set
* SMART feature set
* Mandatory FLUSH CACHE command
* Device Configuration Overlay feature set
* 48-bit Address feature set
Automatic Acoustic Management feature set
SET MAX security extension
* SMART self-test
* SMART error logging
not enabled
not locked
not frozen
not expired: security count
not supported: enhanced erase
HW reset results:
CBLID- above Vih
Device num = 0 determined by the jumper
Checksum: correct
Old 04-13-2005, 04:43 PM   #2
Registered: Mar 2003
Location: Scotland
Distribution: Slackware, RedHat, Debian
Posts: 12,047

Rep: Reputation: 66
Is dma enabled? What do you get from:
hdparm /dev/hdc
Old 04-13-2005, 07:13 PM   #3
LQ Newbie
Registered: Jan 2005
Posts: 3

Rep: Reputation: 0

Your hard drive is performing very well. You should be very pleased with
the results that you received from hdparm -tT.

The 100Mb/S speed that the drive supports is the "interface" speed. That is
the integrated drive electronics maximum theorectical transfer speed.
The electromechanical part of the drive (the HDA or Head Disk Assembly)
cannot transfer data at this speed and will never reach the theoretical

SCSI interfaces can operate at much faster data rates than the highest IDE
speed of 133Mb/S but even they're (better engineered-usually) HDA's can't
supply data quickly enough. In a SCSI system it takes many HDA's operating
through one fast interface to reach the maximum data throughput.

IDE interfaces can only access one HDA at any given time so it is impossible
for the maximum data transfer speed to be reached. SATA may offer some
hope for more SCSI like performance in the future as the standard matures
but until then, SCSI rules for high speed data transfer.

Faster (IDE) interface speeds allow commands and such to be organised more
quickly while allowing the HDA to continue transfering data as efficiently as
possible. Other than that there isn't much advantage.

As an example. If you obtain two identical HDA's and connect one to a 100Mb/S
interface and the other to a 133Mb/S interface and then bench test, you will find
that they perform almost identically. The disks won't spin any faster, nor will
the heads move or settle quicker, only the electroniics is operating at a higher

Hope this helps.

Old 04-13-2005, 09:54 PM   #4
LQ Guru
Registered: Sep 2001
Location: Montreal, Canada
Distribution: Slackware; Debian; Gentoo...
Posts: 2,163

Rep: Reputation: 46
100MB/sec is the maximum in theory... you will never reach that.
You drive is a bit slow (I score 52MB/sec with a 80GB on a 3 years old computer) but this is probably mostly due to your motherboard, not your drive fault, atmo.


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