USB drive has hiccups

bobvanluijt · November 9, 2011, 7:42pm

Hi all,

I’ve attached my USB drive, just working fine…

but…

If I tranfer (over network) to it, it goes, and it stops, it goes and it stops etc.
So a few sec it goes about 2MB p/s and then it stops for a few seconds…

Can somebody help me?

hendersj · November 9, 2011, 8:03pm

On Wed, 09 Nov 2011 18:46:04 +0000, bobvanluijt wrote:

> Hi all,
>
> I’ve attached my USB drive, just working fine…
>
> but…
>
> If I tranfer (over network) to it, it goes, and it stops, it goes and it
> stops etc.
> So a few sec it goes about 2MB p/s and then it stops for a few
> seconds…
>
> Can somebody help me?

This would be fairly normal behaviour - USB2 isn’t very fast relative to
network speeds, so at some point the transfer is paused so the buffers
can be flushed to the disk.

Jim

–
Jim Henderson
openSUSE Forums Administrator
Forum Use Terms & Conditions at http://tinyurl.com/openSUSE-T-C

bobvanluijt · November 9, 2011, 8:08pm

Thanks Jim, but that means that if I increase buffer size it would go faster? Doesn’t it?

robin_listas · November 9, 2011, 8:48pm

On 2011-11-09 20:16, bobvanluijt wrote:
> Thanks Jim, but that means that if I increase buffer size it would go
> faster? Doesn’t it?

In average, no.

–
Cheers / Saludos,

Carlos E. R.
(from 11.4 x86_64 “Celadon” at Telcontar)

hendersj · November 9, 2011, 8:50pm

On Wed, 09 Nov 2011 19:16:02 +0000, bobvanluijt wrote:

> Thanks Jim, but that means that if I increase buffer size it would go
> faster? Doesn’t it?

Not really, because the buffering is between the system and the USB drive

eventually you’ll fill the buffer because USB2 isn’t fast enough, and
at the time the buffer fills, you’ll still have to wait for the data to
flush to the disk.

Jim

–
Jim Henderson
openSUSE Forums Administrator
Forum Use Terms & Conditions at http://tinyurl.com/openSUSE-T-C

bobvanluijt · November 9, 2011, 9:28pm

Hmm, but I just don’t get it.

But then there is something wrong with the write speed.

The write speed is indeed slower then the network speed, but it can’t be THAT slow… There is a lot to find on google, but not a direct solution…

So it goes:
Mac -> Network -> Linuxbuffer -> USB drive

The probleem is in the speed that it goes from the buffer to the drive (correct me if I’m wrong)
There must be something I can do te speed this up, I mean, I know for 100% sure that it isn’t the disk.

Where to search?

hendersj · November 9, 2011, 10:12pm

On Wed, 09 Nov 2011 20:36:08 +0000, bobvanluijt wrote:

> Hmm, but I just don’t get it.
>
> But then there is something wrong with the write speed.

Well, no, probably not.

> The write speed is indeed slower then the network speed, but it can’t be
> THAT slow… There is a lot to find on google, but not a direct
> solution…

How are you defining “that slow”? How long and how frequent are the
pauses?

Is the device a USB2 device or a USB 1.1 device? (Including the USB
controller on the system - if the device is USB2 but the controller only
does 1.1, then you’ll get 1.1 speeds).

> So it goes:
> Mac -> Network -> Linuxbuffer -> USB drive
>
> The probleem is in the speed that it goes from the buffer to the drive
> (correct me if I’m wrong)

Correct. When the buffer fills, then further data coming into the buffer
is paused until the buffer has some free space.

> There must be something I can do te speed this up, I mean, I know for
> 100% sure that it isn’t the disk.

How do you know it isn’t the disk?

Jim

Jim Henderson
openSUSE Forums Administrator
Forum Use Terms & Conditions at http://tinyurl.com/openSUSE-T-C

robin_listas · November 9, 2011, 10:33pm

On 2011-11-09 21:36, bobvanluijt wrote:
>
> Hmm, but I just don’t get it.
>
> But then there is something wrong with the write speed.
>
> The write speed is indeed slower then the network speed, but it can’t
> be THAT slow… There is a lot to find on google, but not a direct
> solution…
>
> So it goes:
> Mac → Network → Linuxbuffer → USB drive

You can do tests to see what is the network speed when writing to memory
(/dev/null). You can check what is the speed from the linux machine to the
usb drive.

Now, is that usb drive a real HD? Or is it a flash device? The second have
slow write speed.

–
Cheers / Saludos,

Carlos E. R.
(from 11.4 x86_64 “Celadon” at Telcontar)

martin_helm · November 9, 2011, 10:35pm

Jim Henderson wrote:
> On Wed, 09 Nov 2011 20:36:08 +0000, bobvanluijt wrote:

>> There must be something I can do te speed this up, I mean, I know for
>> 100% sure that it isn’t the disk.
>
> How do you know it isn’t the disk?

Test the disk with dd with an unbuffered write of a large file, for example
a video like this (of course replace the dummy names with the real names
here)


Pseudocode:
dd oflag=direct if=/home/user/large_file.avi of=/media/disk/large_file.avi