Re: [SLUG] Re: pseudo block device piping to smb or nfs -- MO = { CD-RW, DVD-RW, DVD+RW, etc... }

From: Bryan J. Smith (b.j.smith@ieee.org)
Date: Fri Sep 10 2004 - 13:29:36 EDT

On Fri, 2004-09-10 at 12:59, Eben King wrote:
> DYM 1 every 10^9 _bits_ or 1 every 10^9 _bytes_?

Good question! Actually, I've seen it quoted both ways. But it only
makes a difference of an order of magnitude (one 0).

> Is there any error detection/correction,

Of course not. That adds overhead, hence why DVD-RAM is SLLOOOOWWWW.
The other option is to do a verify after write in software -- now that's
even slower!

Furthermore, traditional MO is only good for 1,000 re-writes. If you
are constantly changing the disc only a little, the area with the
allocation table (FAT-based) or free block list (inode-based) will
quickly get used up.

> or can I expect every full DVD+/-RW I write to start with 25 errors?

??? "Start" with 25 errors? Huh???

The "average" of a device that has an error rate of 1 per billion would
be 5 per 5 billion bytes. It doesn't necessarily mean you will hit it.

-- Bryan

P.S. The minimum ISO9660 Yellow Book (data) track for DVD media is
800MB. That's why it takes a long time to record even a small number of
files. Note, that's for "recording" -- not "packet writing." The
latter doesn't use ISO9660, as ISO9660 is a pre-mastered filesystem.

UDF is the preferred replacement for ISO9660, as it supports being both
a variable size pre-master image (like ISO9660) and a fixed size block
filesystem (like Ext2, FAT, etc...). 

-- 
     Linux Enthusiasts call me anti-Linux.
   Windows Enthusisats call me anti-Microsoft.
 They both must be correct because I have over a
decade of experience with both in mission critical
environments, resulting in a bigotry dedicated to
 mitigating risk and focusing on technologies ...
           not products or vendors
--------------------------------------------------
Bryan J. Smith, E.I.         b.j.smith at ieee.org

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