Oh, I should have added, my compression settings comment only applies to read heavy workloads, as reading 64KB off disk in order to return a handful of bytes is incredibly wasteful by orders of magnitude but doesn’t really cause any problems on write heavy workloads.
> On Jan 5, 2018, at 5:48 PM, Jon Haddad <j...@jonhaddad.com> wrote: > > Generally speaking, disable readahead. After that it's very likely the issue > isn’t in the settings you’re using the disk settings, but is actually in your > Cassandra config or the data model. How are you measuring things? Are you > saturating your disks? What resource is your bottleneck? > > *Every* single time I’ve handled a question like this, without exception, it > ends up being a mix of incorrect compression settings (use 4K at most), some > crazy readahead setting like 1MB, and terrible JVM settings that are the bulk > of the problem. > > Without knowing how you are testing things or *any* metrics whatsoever > whether it be C* or OS it’s going to be hard to help you out. > > Jon > > >> On Jan 5, 2018, at 5:41 PM, Justin Sanciangco <jsancian...@blizzard.com >> <mailto:jsancian...@blizzard.com>> wrote: >> >> Hello, >> >> I am currently benchmarking NVMe SSDs with Cassandra and am getting very bad >> performance when my workload exceeds the memory size. What mount settings >> for NVMe should be used? Right now the SSD is formatted as XFS using noop >> scheduler. Are there any additional mount options that should be used? Any >> specific kernel parameters that should set in order to make best use of the >> PCIe NVMe SSD? Your insight would be well appreciated. >> >> Thank you, >> Justin Sanciangco >
