OT - Journaling File Systems?

[Edwards, Scott (MED, Kelly IT Resouces)]

-----Original Message-----
From: fedora-test-list-bounces at redhat.com
[mailto:fedora-test-list-bounces at redhat.com]On Behalf Of Tom Mitchell
Sent: Tuesday, April 27, 2004 7:24 PM
To: For testers of Fedora Core development releases
Subject: Re: OT - Journaling File Systems?


>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.

It is actually a very simple/basic setup.  It is a Single Board
Computer, 3.0 GHz Pentium 4.  It has 2 IDE connectors and 2 SATA
connectors on the board.  There is a CD-ROM drive pluged into IDE 1
and a single SATA drive plugged into the first SATA port.  No RAID
or anything like that.

The machine is reconfigured at the moment with a IDE drive so I
can't give you the hdparm -I.  I can say that because it thinks it
is a SCSI drive, hdparm won't allow me to turn off the write
caching.

I am curious why FC2 mounts it as a SCSI drive, whereas Knoppix
makes it an IDE drive (hdg).  I am guessing that is a change in
the 2.6 kernel?

>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?

It only has one CPU.  I'm confused about the whole Hyper-Threading
thing, Linux seems to treat it as multiple processors.

>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.

I don't believe that there is any special anything for power fail.
The HD is a Hitachi 164.7GB Deskpro, which I'm pretty sure is just
an off the shelf drive.  I'm trying to get the specs right now. 

>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.

I'm not really sure what the ratio is.  The last few tests I have run
(which have ended up in corrupting the filesystem to the point it
wouldn't even boot) was simply start a 'cp -pirv /etc /tmp' and switch
off the power.

>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...)?

It would be the wall plug.  The scenario I am testing for is someone
tripping over the power cord and accidentally pulling the plug out 
of the wall while it is in operation.

Thanks
  -Scott