Andreas Dilger wrote:
On May 26, 2006 20:49 -0400, Ric Wheeler wrote:
Andreas Dilger wrote:
In a way what you describe is Lustre - it aggregates multiple "smaller"
filesystems into a single large filesystem from the application POV
(though in many cases "smaller" filesystems are 2TB). It runs e2fsck
in parallel if needed, has smart object allocation (clients do delayed
allocation, can load balance across storage targets, etc), can run with
down storage targets.
The approach that lustre takes here is great - distributed systems
typically take into account subcomponent failures as a fact of life &
do this better than many single system designs...
The challenge is still there on the "smaller" file systems that make up
Lustre - you can spend a lot of time waiting for just one fsck to finish ;-)
CFS is actually quite interested in improving the health and reliability
of the component filesystems also. That is the reason for our interest
in the U. Wisconsin IRON filesystem work, which we are (slowly) working
to include into ext3.
We actually were the sponsors of the Wisconsin work, so I am glad to
hear that it has a real impact. I think that the Iron FS ideas will
help, but they still don't eliminate the issues of scalability with fsck
(and some of the scalability issues I see where performance dips with
high object count file systems).
This will also be our focus for upcoming filesystem work. It is
relatively easy to make filesystems with 64-bit structures, but the
ability to run such large filesystems in the face of corruption
environments is the real challenge. It isn't practical to need a
17-year e2fsck time, extrapolating 2TB e2fsck times to 2^48 block
filesystems. A lot of the features in ZFS make sense in this regard.
Cheers, Andreas
--
Absolutely agree - I wonder if there is some value in trying to go back
to profiling fsck if someone has not already done that. It won't get
rid of the design limitations, but we might be able to make some
significant improvements...
ric
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