Re: HD Backup

["Bryan J. Smith" <b.j.smith@ieee.org>]

On Mon, 2006-01-02 at 01:16 -0600, Daniel wrote:
> http://www.fs-driver.org/index.html
> Not going to jump to far into this but 2 guys at work have used this
> and are very pleased.  Don't know about production usablity, but hey a
> step in the write direction.

It's one of the reasons I use Ext2 as a format, instead of Ext3, on a
backup.  So I can read the volumes on any system -- as far back as Linux
2.2 (there was a structural change on Ext2 from 2.0 to 2.2), most
Windows drivers, etc...

-- Bryan

P.S.  Journaling often does _not_ improve data integrity ...

All Ext3 meta-data journaling does is reduce recovery time to make the
filesystem consistent.  It doesn't guarantee any greater integrity of
the data, despite popular belief.  In fact, just like most journaled
filesystems, _only_ a _full_ fsck can do that.  ;->

The only time I've seen Ext3 improve data integrity over Ext2 is when
you put it in full data journaling mode _and_ you use a NVRAM board fir
the journal -- not the hard drive.  Otherwise, dropping down to a full
fsck is the only way to guarantee to 100% absolution that your Ext2/3
filesystem is consistent.

Journaling focuses on improving recovery time, trying to avoid the full
fsck (or what XFS calls a "repair").  It can actually hurt you if
"aggressive" logic is used -- which many of us feel that HPFS, NTFS and
JFS (all IBM designs, not surprisingly) have been guilty of.

Ironically enough, ReiserFS' journaling seems to be very reliable and
not overly aggressive in my experience.  Unfortunately, unlike Ext3 or
XFS (haven't researched JFS' history, although new structures were added
for Linux because it came from OS/2, not AIX), ReiserFS changes in
structure.  That means its off-line fsck tools _must_ be synchronized
with the on-line (kernel) implementation.

That's where I've seen most ReiserFS filesystems get toasted -- at the
fsck, because the user-space tools aren't in-sync with the kernel
implementation.  That's largely due to the fact that ReiserFS' structure
changes.  And it's why I never recommend ReiserFS for removable drives
-- since ReiserFS kernel implementations may vary between systems.


-- 
Bryan J. Smith   mailto:b.j.smith@ieee.org
http://thebs413.blogspot.com
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