Re: Filesystem

From: Anton Ertl (anton_at_mips.complang.tuwien.ac.at)
Date: 02/14/05 

Date: Mon, 14 Feb 2005 15:07:56 GMT

Randy Howard <randyhoward@FOOverizonBAR.net> writes:
>In article <cupmqu$efu$1@nntp.fujitsu-siemens.com>,
>josef.moellers@fujitsu-siemens.com says...
>> AFAIK a journalling filesystem will permit fast startup (no fsck) but
>> cannot prevent data loss in the case of a power failure.

If you want to prevent all data loss (of stuff written to the file
system), you have to run the file system synchronously (very slow).

If what you mean is that journaling only gives you metadata
consistency guarantees (i.e., the directory structure and inode
information will be preserved, but not necessarily the data), you are
right for many journaling file systems.

However, ext3 used to have the data=journal mode which would give data
consistency guarantees (you might lose the last blocks of data
written, but not more). Unfortunately, the last thing I heard about
it is that it is not maintained much anymore, is buggy, and should not
be used.

><sarcasm>
>There is this neat gizmo, called a UPS that will detect the failure,
>and keep your system running temporarily via battery.

Won't prevent power failures from failing power supplies, and
introduces a new type of power failure: the failing UPS. We don't use
UPSs any more because in our experience they are not more reliable than
our mains.

- anton 

-- 
M. Anton Ertl                    Some things have to be seen to be believed
anton@mips.complang.tuwien.ac.at Most things have to be believed to be seen
http://www.complang.tuwien.ac.at/anton/home.html

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