Different IO rates when copying file

I'm trying to use dd to image the parbreastions on an old drive, using the command:

dd if=-dev-hdd4 of=~-tmp-hdd4

The process has been running since about 1:30AM this morning. According to gkrellm,dev-hdd is getting (mostly) sustained transfer rates of 131K-s, while the device on which the destination file resides,dev-hdb, is seeing continuous transfer rates ranging from 4.9MB-s to 6.3MB-s.

What would cause that? From watching the image file grow, the 131K-s number sounds a lot more accurate.

I ran an offline SMART test ondev-hdd before beginning the transfer. Here's the results of a subsequent "smartctl -adev-hdd" :

Some of you might remember my post about trying to get a LaCie internal drive working.smartctl version 5.32 Copyright (C) 2002-4 Bruce Allen

=== START OF INFORMATION SECTION === Device Model: ST310212A Serial Number: 7EG09BDY Firmware Version: 3.02 Device is: Not in smartctl database for details use: -P showall ATA Version is: 5 ATA Standard is: Exact ATA specification draft version not indicated Local Time is: Sat Apr 2 13:47:14 2005 EST SMART support is: Available - device has SMART capability. SMART support is: Enabled

=== START OF READ SMART DATA SECTION === SMART overall-health self-buttessment test result: PbuttED

General SMART Values: Offline data collection status: (0x82) Offline data collection activity was completed without error. Auto Offline Data Collection: Enabled. Self-test end status: ( 0) The previous self-test routine completed without error or no self-test has ever been run. Total time to complete Offline data collection: (2400) seconds. Offline data collection capabilities: (0x1d) SMART execute Offline immediate. No Auto Offline data collection support. Abort Offline collection upon new command. Offline surface scan supported. Self-test supported. No Conveyance Self-test supported. No Selective Self-test supported. SMART capabilities: (0x0003) Saves SMART data before entering power-saving mode. Supports SMART auto save timer. Error logging capability: (0x01) Error logging supported. No General Purpose Logging support. Short self-test routine recommended polling time: ( 2) minutes. Extended self-test routine recommended polling time: ( 14) minutes.

SMART Attributes Data Structure revision number: 16 Vendor Specific SMART Attributes with Thresholds: ID# ATTRIBUTENAME FLAG VALUE WORST THRESH TYPE UPDATED WHENFAILED RAWVALUE 1 RawReadErrorRate 0x0008 091 082 000 Oldage Offline - 85094852 3 SpinUpTime 0x0006 098 098 000 Oldage Always - 0 4 StartStopCount 0x0013 100 100 020 Pre-fail Always - 109 5 ReallocatedSectorCt 0x0013 100 100 036 Pre-fail Always - 22 7 SeekErrorRate 0x0009 058 054 030 Pre-fail Offline - 223372185858 9 PowerOnHours 0x0012 095 095 000 Oldage Always - 4918 10 SpinRetryCount 0x0013 100 100 090 Pre-fail Always - 0 12 PowerCycleCount 0x0013 100 100 000 Pre-fail Always - 109 197 CurrentPendingSector 0x0030 100 100 000 Oldage Offline - 0 198 OfflineUncorrectable 0x0030 100 100 000 Oldage Offline - 0 199 UDMACRCErrorCount 0x000a 200 200 000 Oldage Always - 0

SMART Error Log Version: 1 No Errors Logged

SMART Self-test log structure revision number 1

(-results)

Edited it a bit, to make it fit better in 80 columns. According to the "Offline data collection status", the offline test ran without error. There are 22 relocated sectors, but I can't a mere 22 seeks, over the course of the entire disk, holding down the transfer rate like that.

According to hdparm, the drive is using DMA. The master device on the IDE channel is a 16X DVD-ROM drive, so I'd have to believe there's decent DMA hardware servicing the drive.

What could be wrong? Are there any other diagnostic utilities I can run on it? (Without pulling out the Ultimate Boot CD, that is.)