On Mon, Nov 5, 2018 at 8:31 PM Raghavendra Gowdappa <[email protected]> wrote:
> > > On Tue, Nov 6, 2018 at 9:58 AM Vijay Bellur <[email protected]> wrote: > >> >> >> On Mon, Nov 5, 2018 at 7:56 PM Raghavendra Gowdappa <[email protected]> >> wrote: >> >>> All, >>> >>> There is a patch [1] from Kotresh, which makes ctime generator as >>> default in stack. Currently ctime generator is being recommended only for >>> usecases where ctime is important (like for Elasticsearch). However, a >>> reliable (c)(m)time can fix many consistency issues within glusterfs stack >>> too. These are issues with caching layers having stale (meta)data >>> [2][3][4]. Basically just like applications, components within glusterfs >>> stack too need a time to find out which among racing ops (like write, stat, >>> etc) has latest (meta)data. >>> >>> Also note that a consistent (c)(m)time is not an optional feature, but >>> instead forms the core of the infrastructure. So, I am proposing to merge >>> this patch. If you've any objections, please voice out before Nov 13, 2018 >>> (a week from today). >>> >>> As to the existing known issues/limitations with ctime generator, my >>> conversations with Kotresh, revealed following: >>> * Potential performance degradation (we don't yet have data to >>> conclusively prove it, preliminary basic tests from Kotresh didn't indicate >>> a significant perf drop). >>> >> >> Do we have this data captured somewhere? If not, would it be possible to >> share that data here? >> > > I misquoted Kotresh. He had measured impact of gfid2path and said both > features might've similar impact as major perf cost is related to storing > xattrs on backend fs. I am in the process of getting a fresh set of > numbers. Will post those numbers when available. > > I observe that the patch under discussion has been merged now [1]. A quick search did not yield me any performance data. Do we have the performance numbers posted somewhere? Thanks, Vijay [1] https://review.gluster.org/#/c/glusterfs/+/21060/
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