Golden advice. Thank you Greg On Mon, Jul 16, 2018 at 1:45 PM, Gregory Farnum <[email protected]> wrote:
> On Fri, Jul 13, 2018 at 2:50 AM Robert Stanford <[email protected]> > wrote: > >> >> This is what leads me to believe it's other settings being referred to >> as well: >> https://ceph.com/community/new-luminous-rados-improvements/ >> >> *"There are dozens of documents floating around with long lists of Ceph >> configurables that have been tuned for optimal performance on specific >> hardware or for specific workloads. In most cases these ceph.conf >> fragments tend to induce funny looks on developers’ faces because the >> settings being adjusted seem counter-intuitive, unrelated to the >> performance of the system, and/or outright dangerous. Our goal is to make >> Ceph work as well as we can out of the box without requiring any tuning at >> all, so we are always striving to choose sane defaults. And generally, we >> discourage tuning by users. "* >> >> To me it's not just bluestore settings / sdd vs. hdd they're talking >> about ("dozens of documents floating around"... "our goal... without any >> tuning at all". Am I off base? >> > > Ceph is *extremely* tunable, because whenever we set up a new behavior > (snapshot trimming sleeps, scrub IO priorities, whatever) and we're not > sure how it should behave we add a config option. Most of these config > options we come up with some value through testing or informed guesswork, > set it in the config, and expect that users won't ever see it. Some of > these settings we don't know what they should be, and we really hope the > whole mechanism gets replaced before users see it, but they don't. Some of > the settings should be auto-tuning or manually set to a different value for > each deployment to get optimal performance. > So there are lots of options for people to make things much better or much > worse for themselves. > > However, by far the biggest impact and most common tunables are those that > basically vary on if the OSD is using a hard drive or an SSD for its local > storage — those are order-of-magnitude differences in expected latency and > throughput. So we now have separate default tunables for those cases which > are automatically applied. > > Could somebody who knows what they're doing tweak things even better for a > particular deployment? Undoubtedly. But do *most* people know what they're > doing that well? They don't. > In particular, the old "fix it" configuration settings that a lot of > people were sharing and using starting in the Cuttlefish days are rather > dangerously out of date, and we no longer have defaults that are quite as > stupid as some of those were. > > So I'd generally recommend you remove any custom tuning you've set up > unless you have specific reason to think it will do better than the > defaults for your currently-deployed release. > -Greg > > >> >> Regards >> >> On Thu, Jul 12, 2018 at 9:12 PM, Konstantin Shalygin <[email protected]> >> wrote: >> >>> I saw this in the Luminous release notes: >>>> >>>> "Each OSD now adjusts its default configuration based on whether the >>>> backing device is an HDD or SSD. Manual tuning generally not required" >>>> >>>> Which tuning in particular? The ones in my configuration are >>>> osd_op_threads, osd_disk_threads, osd_recovery_max_active, >>>> osd_op_thread_suicide_timeout, and osd_crush_chooseleaf_type, among >>>> others. Can I rip these out when I upgrade to >>>> Luminous? >>>> >>> >>> This mean that some "bluestore_*" settings tuned for nvme/hdd separately. >>> >>> Also with Luminous we have: >>> >>> osd_op_num_shards_(ssd|hdd) >>> >>> osd_op_num_threads_per_shard_(ssd|hdd) >>> >>> osd_recovery_sleep_(ssd|hdd) >>> >>> >>> >>> >>> k >>> >>> >> _______________________________________________ >> ceph-users mailing list >> [email protected] >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> >
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