Solved Re: [Dirvish] slow writing to external USB2 hard disc

[Gert Brinkmann]

Gert Brinkmann wrote:

> hard disc is connected to an USB2 controller. The Problem: data transfer
> is very slow. It makes approx. 1 MByte/s only, but it should be more
> than 20 MByte/s. The hard disc is formatted as ext3fs and is mounted as
> 
>> /dev/sde2 on /media/bak1 type ext3 (rw,nosuid,nodev,sync,noatime,data=ordered)

The problem is the "sync"-option the hard disc is mounted automatically
with. If I am using async mode via

  mount -o remount,async /media/bak1

copying becomes _much_ faster:

sync; time (rsync foo /media/bak1/test/;sync)
real    0m5.974s

sync; time (cp foo /media/bak1/test/;sync)
real    0m3.934s

So data transfer is more than 25 MB/s. This is ok. Even if you shorten
the commit-interval from 5 seconds to 1 second...

  mount -o remount,commit=1 /media/bak1

... the speed is that high.


There are, as I think two problems somewhere in Linux:

1) udev (or which layer ever) should mount drives with async,commit=1 as
default instead of using the extremely slow sync mode.

2) I understand that sync is slower than async, but IMHO it is a bug,
that it takes more than 20 times longer!?

Does anybody know if it does make sense to report these two things
somewhere? If so, where would it be best?

Greetings,
Gert