Re: stable xfs

[Ming Zhang <mingz@ele.uri.edu>]

On Tue, 2006-07-18 at 22:56 -0700, Chris Wedgwood wrote:
> 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

right

> 
> > 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.
> 

i mean with UPS and huge write cache, but no write barrier.

> 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