Peter Salisbury wrote:
> On Wednesday 04 Jul 2007, Chris Dennis wrote:
>> Peter Salisbury wrote:
>>> Hi,
> 8<
>>> On top of this, I only get 1MB/s with a udf file system on the
>>> DVD-RAM and the Linux udf system won't handle a file over 1GB.
>>> When I put an ext2 file system on the DVD-RAM the average
>>> transfer speed falls to 0.7MB/s.
>>>
>>> Is it really this bad? Has anyone had a better experience of
>>> DVD-RAM?
>> Hello Peter
>>
>> I use DVD-RAMs for backups via Amanda, which reports a write speed
>> of about 1100KBps on Panasonic '2-3x speed' discs.
>>
>> A quick test:
>>
>> $ time (dd if=/dev/zero of=/media/dvdram/2G bs=4096 count=524288;
>> umount /media/dvdram)
>> 524288+0 records in
>> 524288+0 records out
>> 2147483648 bytes (2.1 GB) copied, 958.001 seconds, 2.2 MB/s
>>
>> real 22m49.100s
>> user 0m0.108s
>> sys 0m3.132s
>>
>> shows a throughput of 1.5MBps including the time to unmount the
>> disk. gkrellm was showing a transfer rate of about 1.5MBps while
>> that was running.
>>
>> I don't know if DVD-RAMs are supposed to run faster than that or
>> not.
>
> Thanks Chris,
>
> I've reformatted the DVD-RAM disk to fat32 and that seems to be the
> best performing of {ext2, udf, fat32} (can't believe I'm saying
> this!) coming in at about 1.5MB/s for a 100MB transfer. That seems to
> tally closely with your Amanda experience so I guess that's just the
> way it is.
I forgot to mention that I use ext2 on my DVD-RAMs.
And I've been having a lot of trouble with that lately -- running
e2fsck -fy
on a DVD-RAM seems to make it instantly unusable. It used to work fine
on my old PC, with an IDE DVD-RAM drive. Now I've got a SATA DVD-RAM
drive attached to 64-bit Debian it's much worse! Maybe I should raise a
bug report...
>
> That's about 37.5% of the advertised performance of the setup. Ah
> well...
>
> In case anyone isn't put off DVD-RAM and wants to format the disks for
> fat32 there is a small hurdle in that you get this warning:
>
> unable to get drive geometry, using default 255/63
Perhaps there's a clue there to my ext2 problems -- fdisk reports
different geometry on my old and new systems.
>
> so you have to specify quite a few parameters to get a mountable file
> system:
>
> mkdosfs -I -F 32 -s 128 -S 2048 /dev/hdx
>
> (the -s 128 was just a guess but it WFM!)
>
> HTH, Peter
>
cheers
Chris
--
Chris Dennis cgdennis@???
Fordingbridge, Hampshire, UK
