transfer rate from hd to hd slows right down!

[mansat]

Hi Guys,

Just wondering if anyone knew the cause to transfer rates slowing right down in windows.

I have 10 x 1gb files. I am copying and pasting them from one drive to another.

Speed starts off at 1.2GB per second, then 600MB, then 300, 200, 100 and then at about half way through it sits at about 60 till it finishes.

Does anyone know why this happens? I want 1.2GB the whole time!

Any ideas ?

thanks!

 

[zigzag3143]

Hi Guys,

Just wondering if anyone knew the cause to transfer rates slowing right down in windows.

I have 10 x 1gb files. I am copying and pasting them from one drive to another.

Speed starts off at 1.2GB per second, then 600MB, then 300, 200, 100 and then at about half way through it sits at about 60 till it finishes.

Does anyone know why this happens? I want 1.2GB the whole time!

Any ideas ?

thanks!

How are you transferring them. USB, wifi, ethernet, etc?

 

[essenbe]

Whatever you are using, transfer speed normally does that when transfering multiple files. Try with 1 file or take the 10 1GB fikes and zip them into 1 file and transfer that. See what your readings are then.

Also, your transfer speeds are also limited by the drive you are transfering to. No matter how fast you are able to transfer, the receiving drive can only write so fast. You may want to run a test on the hard drives to determine their max rates, both read and write.

 

[GeneO]

That sounds about right for disk to disk. It usually is about 1/2 the slowest drive speed. The estimate of the speed starts out optimistic. You can't expect a rate that is faster than a disk drive can deliver.

 

[karlsnooks]

MikeMeadUK,

Let us know the answer to ZigZag's question please.

 

[Britton30]

Here is what I get using USB with a SATA II drive.

 

[essenbe]

Here is what I get using USB with a SATA II drive.
View attachment 164397

I don't think you should get the same reading on 2.0 and 3.0

 

[Britton30]

I often copy or move files off my HDD to a USB attached HDD or flash drive. I have the same experience. Starts real fast and slows until finished. If you are running GB/s speed, that is very fast. Mine starts out at about 150MB/s.

 

[essenbe]

Gary's right. These are the transfer speeds on my system

​

 

[mansat]

Hi, I am transfering them from internal drives using SATA2 drives 7200rpm.

It does actually transfer at around 600MB per second, because when I transfer all 10 over to the other drive, the first 1GB file finishes in about 2 seconds and I can open it up etc and its all fine, the next file takes longer, and the 3rd takes even longer etc etc.

Not sure why its fast to start with and then slows off

 

[GeneO]

Hi, I am transfering them from internal drives using SATA2 drives 7200rpm.

It does actually transfer at around 600MB per second, because when I transfer all 10 over to the other drive, the first 1GB file finishes in about 2 seconds and I can open it up etc and its all fine, the next file takes longer, and the 3rd takes even longer etc etc.

Not sure why its fast to start with and then slows off

The first is probably cached in memory and not fully flushed to disk yet and when you read it, you are reading it from the memory cache. As your memory cache fills with the backlog of writes, you slowi down to the drive rate

7200 rpm disks can only do about 150 MB/s maximum, and their onboard cache is limited to about 64 MB - you cannot write at 600MB/s to disk with that large of a file.

 

[mansat]

Ah ha! That makes sense!

So why does it not do this for all 10 files? I have 16GB of memory so 10GB will be easily doable?

cheers

 

[GeneO]

The cache is of limited size. I don;t know what it is offhand.

I am not sure I believe my explanation. I will have to think about it a little more. I am sure that if the file is in memory you can read it back from there, but I think it would need to be flushed to disk before you can read it.

 

[karlsnooks]

your fastest transfers will be when you use RoboCopy to transfer files.

Robocopy is a command built into Win 7.

 

[GeneO]

That sounds about right for disk to disk. It usually is about 1/2 the slowest drive speed. The estimate of the speed starts out optimistic. You can't expect a rate that is faster than a disk drive can deliver.

No, think I was right. I don;t believe a write flush to disk is required before reading the file from cache.