On Sat, Sep 26, 2009 at 8:13 AM, Jeff Layton <[email protected]> wrote: > It will only stop the clean up of checkpoints outside of policy - correct? > So it won't stop them from being created but it will stop the cleaning > process. > It will completely stop cleaning checkpoints, which is what is consuming drive I/O. Checkpoints in themselve don't use much ressources, cleaning them however does.
> > Understood. But for benchmarks like IOzone where you are creating > files and most likely syncing, this will trigger a checkpoint. I haven't > looked too much at IOzone but it might even be causing a sync after > each record right, again forcing a checkpoint. > > So I was looking for some way to control how often checkpoints are > created - something like the protection_period option for the GC. But > I understand that the checkpoint is a part of the design of the file system. > Checkpoints are created each time a change is commited to disk right, but creating a checkpoint does not take much system ressources, try time'ing mkcp, it won't use any ressources, it just writes a marker at the end of the disk to say that all that is written behind it is good to use if a crash happens or the user wants to mount the partition in the past. Increasing checkpoint period would just increases the risk of losing more data on crash with minimal or no performance gain. I don't know if you ever worked with shadow copies in Windows but creating a shadow copie would consume lots of drive I/O and CPU, that is because NTFS wasn't conceived as a log filesystem like NILFS and must write structures and files to the disk for whatever changes happened to the disk, it must also freeze the filesystem and make sure all writes are atomic before creating the snapshot. While NILFS just write a checkpoint each time it knows the last write is complete, converting a checkpoint to a snapshot then is just a matter of changing a flag so the GC won't remove it afterward. _______________________________________________ users mailing list [email protected] https://www.nilfs.org/mailman/listinfo/users
