On Fri, Oct 23, 2009 at 7:19 PM, Adam Leventhal <a...@eng.sun.com> wrote:
> On Fri, Oct 23, 2009 at 06:55:41PM -0500, Tim Cook wrote: > > So, from what I gather, even though the documentation appears to state > > otherwise, default checksums have been changed to SHA256. Making that > > assumption, I have two questions. > > That's false. The default checksum has changed from fletcher2 to fletcher4 > that is to say, the definition of the value of 'on' has changed. > > > First, is the default updated from fletcher2 to SHA256 automatically for > a > > pool that was created with an older version of zfs and then upgraded to > the > > latest? Second, would all of the blocks be re-checksummed with a zfs > > send/receive on the receiving side? > > As with all property changes, new writes get the new properties. Old data > is not rewritten. > > Adam > > Adam, Thank you for the correction. My next question is, do you happen to know what the overhead difference between fletcher4 and SHA256 is? Is the checksumming multi-threaded in nature? I know my fileserver has a lot of spare cpu cycles, but it would be good to know if I'm going to take a substantial hit in throughput moving from one to the other. --Tim
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