This has not been my experience… In my benchmarks over the years noatime has mattered.
However, I might have not been as scientifically motivated to falsify the noatime hypothesis… specifically, I might just have accidentally used confirmation bias and assumed that noatime mattered and then moved on. A real benchmark would work :) On Mon, May 19, 2014 at 11:53 AM, Bryan Talbot <bryan.tal...@playnext.com>wrote: > For XFS, using noatime and nodirtime isn't really useful either. > > > http://xfs.org/index.php/XFS_FAQ#Q:_Is_using_noatime_or.2Fand_nodiratime_at_mount_time_giving_any_performance_benefits_in_xfs_.28or_not_using_them_performance_decrease.29.3F > > > > > On Sat, May 17, 2014 at 7:52 AM, James Campbell < > ja...@breachintelligence.com> wrote: > >> Thanks for the thoughts! >> On May 16, 2014 4:23 PM, Ariel Weisberg <ar...@weisberg.ws> wrote: >> Hi, >> >> Recommending nobarrier (mount option barrier=0) when you don't know if a >> non-volatile cache in play is probably not the way to go. A non-volatile >> cache will typically ignore write barriers if a given block device is >> configured to cache writes anyways. >> >> I am also skeptical you will see a boost in performance. Applications >> that want to defer and batch writes won't emit write barriers frequently >> and when they do it's because the data has to be there. Filesystems depend >> on write barriers although it is surprisingly hard to get a reordering that >> is really bad because of the way journals are managed. >> >> Cassandra uses log structured storage and supports asynchronous periodic >> group commit so it doesn't need to emit write barriers frequently. >> >> Setting read ahead to zero on an SSD is necessary to get the maximum >> number of random reads, but will also disable prefetching for sequential >> reads. You need a lot less prefetching with an SSD due to the much faster >> response time, but it's still many microseconds. >> >> Someone with more Cassandra specific knowledge can probably give better >> advice as to when a non-zero read ahead make sense with Cassandra. This is >> something may be workload specific as well. >> >> Regards, >> Ariel >> >> On Fri, May 16, 2014, at 01:55 PM, Kevin Burton wrote: >> >> That and nobarrier… and probably noop for the scheduler if using SSD and >> setting readahead to zero... >> >> >> On Fri, May 16, 2014 at 10:29 AM, James Campbell < >> ja...@breachintelligence.com> wrote: >> >> Hi all— >> >> >> >> What partition type is best/most commonly used for a multi-disk JBOD >> setup running Cassandra on CentOS 64bit? >> >> >> >> The datastax production server guidelines recommend XFS for data >> partitions, saying, “Because Cassandra can use almost half your disk space >> for a single file, use XFS when using large disks, particularly if using a >> 32-bit kernel. XFS file size limits are 16TB max on a 32-bit kernel, and >> essentially unlimited on 64-bit.” >> >> >> >> However, the same document also notes that “Maximum recommended capacity >> for Cassandra 1.2 and later is 3 to 5TB per node,” which makes me think >> >16TB file sizes would be irrelevant (especially when not using RAID to >> create a single large volume). What has been the experience of this group? >> >> >> >> I also noted that the guidelines don’t mention setting noatime and >> nodiratime flags in the fstab for data volumes, but I wonder if that’s a >> common practice. >> >> James >> >> >> >> >> -- >> >> >> Founder/CEO Spinn3r.com >> Location: *San Francisco, CA* >> Skype: *burtonator* >> blog: http://burtonator.wordpress.com >> … or check out my Google+ >> profile<https://plus.google.com/102718274791889610666/posts> >> <http://spinn3r.com> >> War is peace. Freedom is slavery. Ignorance is strength. Corporations >> are people. >> >> >> > > > -- > Bryan Talbot > Architect / Platform team lead, Aeria Games and Entertainment > Silicon Valley | Berlin | Tokyo | Sao Paulo > > -- Founder/CEO Spinn3r.com Location: *San Francisco, CA* Skype: *burtonator* blog: http://burtonator.wordpress.com … or check out my Google+ profile<https://plus.google.com/102718274791889610666/posts> <http://spinn3r.com> War is peace. Freedom is slavery. Ignorance is strength. Corporations are people.
