Kirk Bocek wrote:
Feizhou wrote:
Run XFS without write caching and you should be safe. Are you
creating thousands of files?
I'd still like to know what you mean by 'without write caching.' Do you
mean setting it on the 3Ware or is there a FS or OS setting you are
talking about?
There are two levels of caching. Hardware and software. Hardware level
caching involves in your case the 3ware card cache and the individual
disk caches.
Software level involves the kernel's disk cache.
There are FS level settings available. You can mount the filesystem with
the sync option which means writes are to be done synchronously and so
these are not stored in the kernel's cache. There is also dirsync which
can to used to ensure metadata on files/directories are also written
synchronously.
You can also do it on a per file level by setting the file's sync (S)
attribute.
So a completely paranoid setup would include making sure that the
file/filesystem is sync'ed and also turning off the write cache on the
hardware. You should be able to set sync at the software level and leave
the hardware write caching on and see a difference.
You can use Bruce Guenter's framework and test the differences. His is
pretty simple and you can take out those filesystems that you do not
want to test.
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