On Tue, Jul 18, 2006 at 09:20:44PM -0400, Ming Zhang wrote:
> when u say large parallel storage system, you mean independent
> spindles right? but most people will have all disks configured in
> one RAID5/6 and thus it is not parallel any more.
it depends, you might have 100s of spindles in groups, you don't make
a giant raid5/6 array with that many disks, you make a number of
smaller arrays
> i think with write barrier support, system without UPS should be ok.
with barrier support a UPS shouldn't be necessary
> considering even u have UPS, kernel oops in other parts still can
> take the FS down.
but a crash won't cause writes to be 'reordered'
reordering is bad because the fs pushes writes down in a manner that
means when it comes back it will be able to make it self consistent,
so if you have a number of writes pending and some of them are lost,
and those that are lost are not the most recent writes because of
reordering, you can end up with a corrupt fs
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