Subject: Re: [linux-audio-user] Disks
From: Chris Pickett (chris.pickett_AT_mail.mcgill.ca)
Date: Thu Jun 10 2004 - 22:17:29 EEST
Juhana Sadeharju wrote:
>>From: Malcolm Baldridge <linux-audio_AT_paypc.com>
>>Subject: Re: [linux-audio-user] Ardour, Jack, and 2.6 kernels + XRuns
>> with the Audiophile 24/96 M-Audio
>>
>>1) You can't use more than one drive per IDE channel.
>
> [ ... ]
>
>>It's VERY bad on performance to mix very slow devices (such as CD-ROMs)
>>with fast ones: they hold a lock on the bus during all operations,
>
>
> I recently removed CD-ROM device completely. I ended up doing that
> because I got disk errors. The disks are perfectly ok, however.
> Some example symptoms were:
> -When the CD-ROM device slided in the disk, Alsa audio play was
> interrupted for 7 seconds
> -File copy sometimes made errors -- such as the highest bit of one
> byte of 300 MB file turned from 0 to 1
> -File was temporarily corrupted -- error stayed at the same place,
> no matter how many times the file was verified; after the boot,
> the file was again ok; I made sure the caches were emptied, and so,
> it looks like a certain bit pattern or certain address caused the
> change in data
>
> I'm still testing and waiting for errors to happen.
>
> This problem has driven me to verify that files are copied ok,
> that the created tar.bz2 packages are ok (both the tar.bz2 file
> and its content). I also have set Emacs to make the numbered backup
> copies and make them by moving (not by copying). Backups, flac, mp3
> and ogg codings need to be verified too.
>
> The point is this: how you would know about the rare bit changes
> if you never verify the files?
>
> In audio work such a bit changes can go unnoticed. How many of you
> verify, e.g., that a simple edit to a file did not made a bit error?
> I'm sure that no one verifies. Use of a dither makes the detection
> quite hard.
I would be interested in a filesystem that computed checksums in the
background every time a file was copied and reperformed bad copies, but
this sounds like it could be a substantial hit on performance. I wonder
if we'll ever see something like this, or if something already exists even.
Chris
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