On Mon, Jul 21, 2014 at 4:53 PM, Warren Young <war...@etr-usa.com> wrote:
> I also don't see that this feature buys you anything if you're on a system > with reliable fsync(). Say, a Linux box running XFS with write barriers > enabled, with the filesystem stored on a storage subsystem that doesn't lie > about whether it has flushed the data to disk. That means something like a > real hardware RAID card with battery-backed cache RAM, for example, rather > than a consumer-grade HDD connected to your gaming mobo's on-board SATA > connector. > The read-back-before-commit checks would catch problems related to a lying FS. Before fossil commits any new artifacts, it makes sure that everything it just wrote to the db can be read back from it. The R-card part (the really expensive part) is another level of hash checking added on top of the manifests having unique hashes. -- ----- stephan beal http://wanderinghorse.net/home/stephan/ http://gplus.to/sgbeal "Freedom is sloppy. But since tyranny's the only guaranteed byproduct of those who insist on a perfect world, freedom will have to do." -- Bigby Wolf
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