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
