Do you have some detailed benchmark metrics? Like the QPS, Avg read/write latency, P95/P99 read/write latency?
On Fri, Jan 5, 2018 at 5:57 PM, Justin Sanciangco <jsancian...@blizzard.com> wrote: > I am benchmarking with the YCSB tool doing 1k writes. > > > > Below are my server specs > > 2 sockets > > 12 core hyperthreaded processor > > 64GB memory > > > > Cassandra settings > > 32GB heap > > Concurrent_reads: 128 > > Concurrent_writes:256 > > > > From what we are seeing it looks like the kernel writing to the disk > causes degrading performance. > > > > > > Please let me know > > > > > > *From:* Jeff Jirsa [mailto:jji...@gmail.com] > *Sent:* Friday, January 5, 2018 5:50 PM > *To:* email@example.com > *Subject:* Re: NVMe SSD benchmarking with Cassandra > > > > Second the note about compression chunk size in particular. > > -- > > Jeff Jirsa > > > > > 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> > 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 > > > > -- Dikang