[Beowulf] Re: RAID for home beowulf

[Chris Samuel]

Hi Mark,

----- "Mark Hahn" <hahn at mcmaster.ca> wrote:

> AFAIKT, it's just an option for the default mount
> config now that wasn't offered before.

The kernel config option CONFIG_EXT3_DEFAULTS_TO_ORDERED
is not set by default in Linus's git tree.  The changes
were introduced in 2.6.30.

That release also sets the default atime settings (for
all filesystems I believe) to relatime, you need a mount
command that understands the strictatime option to be able
to change that one.

> major distros (I only checked fedora) still do
> data=ordered, and the latest kernel snapshot
> still has data=ordered as the default.

Sounds like they've changed the kernel defaults.

> the kernel config help text points to this:
> http://ext4.wiki.kernel.org/index.php/Ext3_Data%3DOrdered_vs_Data%3DWriteback_mode
> which makes a useful point about app-level consistency still requiring
> fsyncs (which operates above any fs-level consistency guarantees.)

Oh indeed - Ted T'so apologised for his part in
ext3's data=ordered mode at the Linux Storage and
Filesystem workshop 2009.

 http://lwn.net/Articles/327601/

Look for "Rename, fsync, and ponies". :-)

cheers!
Chris
-- 
Christopher Samuel - (03) 9925 4751 - Systems Manager
 The Victorian Partnership for Advanced Computing
 P.O. Box 201, Carlton South, VIC 3053, Australia
VPAC is a not-for-profit Registered Research Agency