OT - Journaling File Systems?

[Tom Mitchell]

On Tue, Apr 27, 2004 at 12:03:35PM -0500, Edwards, Scott (MED, Kelly IT Resouces) wrote:
> Does anyone know of any comparisons of ext3, jfs, xfs and reiser for
> reliability?
....
> Next I tried XFS.  I was excited at first because a normal bootup was
> only 18 seconds.  The first reboot after a 'plug pull' was only 27
> seconds (and I think that included the 5 second wait).  I was very
> excited to see this improvement over ext3.  However, it was short lived.
> After the second 'plug pull' it took 1 minute and 16 seconds to boot.
> But it claimed corrupted metadata and that the superblock was trashed
> and could not even mount the partiton.

Can you tell us (me) more about the hardware and test setup.....

Disks, Single or multiple disk in system, Raid?, controllers,
partition, SCSI, EIDE, FC, SIDE, cable width, speed, DMA
tagged-queuing depth, hdparm -I, Buffer modes in the disk and
controller, read buffers, write buffers, mkfs options.

XFS requires effective atomic and strictly ordered writes for meta
data consistency.  In multiple processor environments strong mutual
exclusion locks are a requirement.  I suspect that this is true for 
all file systems.  Is this a multiprocessor box?

Any 'plug pull' safe disk needs some sort of hardware logic to sense
power failure, then self-power long enough to finish the committed
writes and not start others.  Does the power supply signal the system
with a power-fail line? Does the mother board signal the OS with a
power-fail interrupt?  The more RAM on the disk dedicated for write
buffering the more interesting the write buffer issues on the disk
are.

What is the ratio of data to meta data in your test.  XFS can allocate
lots of data blocks for data and be lazy with the meta data.  This
implies that the data read from a file after a failure will be correct
or simply absent in part depending on how it was written.  This ratio
with the meta data sync time etc. can define the number of faces on
the die in terms of how often meta-data will be be corrupt.

Are you pulling the power plug on the disk (DC,5V,12V), disk box (AC) or the
wall plug (AC) for the entire system (disk,MB,processor,DRAM...)?


-- 
	T o m  M i t c h e l l 
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