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.
>> On Jan 5, 2018, at 5:41 PM, Justin Sanciangco <jsancian...@blizzard.com
>> <mailto:jsancian...@blizzard.com>> wrote:
>> 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