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. [cid:image001.png@01D3864E.B5034DA0] Please let me know From: Jeff Jirsa [mailto:jji...@gmail.com] Sent: Friday, January 5, 2018 5:50 PM To: user@cassandra.apache.org 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<mailto: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
