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Extremely slow transfer speed between internal drives : < 2MB/s !

Last response: in Storage
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August 3, 2011 11:02:14 PM

I am being hunted by ghostly slow transfer rates while copying files between my two internal drives. Sometimes as slow as 2 MB/s!!!
It happens when I copy few thousand files from various folders (say ~1000 files totaling ~200MB in each folder). Some folders are copied instantly at 120MB\s, as it should be. But in general the transfer speed stars ok and sooner or later falls down to 15MB/s, 10MB/s and even 2MB/s. No issues while copying large files like videos.
Both drives are SATA-III, fresh installed on my self-build rig, NTFS partitions, running in AHCI mode under Win7_64.
S.M.A.R.T test indicate no issues and both drives perform individually at 140-150MB/s (HD-Tune).
According to Device Manager, one is in UltraDMA Mode 6 and the other in UltraDM Mode 5, so there is no fallback to PIO mode. CPU utilization is 1-2% while copying. Antivirus disabled just in case. No other software running, no RAID.
Tried deleting ATA Channels to force the OS to detect and reinstall SATA drivers. Same issue.
Tried switching cables and moving one drive to SATA-II port. Same problem.
Fragmentation could be the case, but both drives are brand new, barely used, and OS installation is less than 1 month old. Hard to believe they could get fragmented in such short time.

Any help is more than appreciated. Pulling my hair off!

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ASUS P8P67 LE rev 3
Intel Core i7-2600K, no overclocking
8 GB RAM PC1066
GeForce GTX 560 TI
HD 1 : Hitachi 2TB 7200/64MB/SATA-III
HD 2 : Seagate 2TB 5900/64MB/SATA-III
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a b G Storage
August 4, 2011 12:55:19 AM

If large files are copying fast but larger numbers of smaller files copy slowly, I bet you are simply seeing the lag generated by all the changes to the filesystem. Every time you copy an individual file, several requests are made to NTFS to filesystem for the original file and the new file. Each request takes some amount of time to happen. When you copy a large file, only 1 request at the begning and the end of the copy is made.

The below math isn't EXACTLY correct but will give you an idea of what I'm talking about.

(1) 200MB file with disks with 10ms access time and 200MB/s between drives

10ms - request to locate file
1s - Copy 200MB
10ms - write file system location

Total - 1s 20ms - almost 200MB/sec


(1000) 200k files with disks with 10ms access time and 200MB/s between drives

10ms - request to locate file
10ms - Copy 200k
10ms - write file system location
10ms - request to locate file
10ms - copy 200k
10ms - write file system location

....
....
....

Total= 30ms X 1000 files=30secs

200MB/30secs= 6.67MB/sec



Does that make sense? If you were to image the drive or copy at the block level rather than the file level, then you would get your 200MB/sec
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August 4, 2011 7:16:22 PM

Thanks for the math tokencode. I work on statistics so I know what you are talking about.
However real world is strange place. Now I have installed Win7 on both drives, so I get to choose which drive I want to boot from the BIOS.
Booting Hitachi (drive 1) and copying from Seagate (drive 2) into drive 1 shows the same slow speed.
Booting Seagate and copying (same files of course) to Hitachi drive works blazing fast, i.e. at the usual HDD speeds.

Still thinking....
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a c 316 G Storage
August 6, 2011 11:15:22 PM

How do the drives perform if you copy between two folders on the same drive?
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