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Re: Problem identified: WAPL/RAIDframe performance problems

On Sat, Dec 01, 2012 at 11:38:55PM -0500, Mouse wrote:
 > >>> things.  What I care about is the largest size "sector" that will (in
 > >                                     ^^^^^^^
 > >>> the ordinary course of things anyway) be written atomically.
 > >> Then those are 512-byte-sector drives [...]
 > > No; because I can do 4K atomic writes, I want to know about that.
 > And, can't you do that with traditional drives, drives which really do
 > have 512-byte sectors?  Do a 4K transfer and you write 8 physical
 > sectors with no opportunity for any other operation to see the write
 > partially done.  Is that wrong, or am I missing something else?

Insert a kernel panic (or power failure(*)) after five sectors and
it's not atomic. One sector, at least in theory(*), is.

(*) let's ignore for now the various daft things that disks sometimes
do in practice.

David A. Holland

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