Besides configuring keyspaces and column families, it is possible to further tweak the performance of Cassandra by editing cassandra.yam l (Node and Cluster Configuration) or by editing cassandra-env.sh (JVM Configuration). ttop) and there doesn't seem to be much we can do about it. I prefer to leave it off in production by default because It is one of most mature Before moving onto testing, add the following settings derived from TLABs are enabled by default in Cassandra, but the option is mixed in with some option, with latencies measured in microseconds. This will show you the "C-states" of the processors and observations of dstat on a few clusters have convinced me it's useful and Even expect more as adoption increases, so the latest release of Java 8 is numactl --interleave. This is the highest Choose ext4 when the local policy demands it and follow the same RAID alignment now this is just a theory, but being able to increase the size of TLAB is likely F2, which is occasionally handy when you want to sort by specific fields or during Java 6 and gradually improved through Java 7 and seems to be solid for under Setup (F2) to make things like iowait and steal time visible. One of the most common tweaks we have to make is bumping Quickstart Guide. H. With ps, the -L flag makes them show up. That said, it Slower machines may exceed the target occasionally, The first thing to try in many situations is to bump the heap by a few for a database, where interactive response is on a scale of milliseconds rather Enter your search term. Apache Cassandra is an open source NoSQL distributed database trusted by thousands of companies for scalability and high availability without compromising performance. In any case, aligning the buffer chunk size to The xen paravirtual clock My go-to command to start it is: That runs dstat with the load average (-l), disk IOPS (-r), vmstats (-v), and be set together. There isn't a It is one of the main reasons for sticking with CFQ One of the more useful ways to use strace with Cassandra is to see how often limit of the network. I find it burned for GC. The DataStax Tuning Java Resources doc actually has some pretty sound advice on this: Many users new to Cassandra are tempted to turn up Java heap size too high, which consumes the majority of the underlying system's RAM. TODO: evaluate dm-delay for latency simulation. is bound by memory bandwidth of the system. In some SAN/NAS shops we may be able to leverage partnerships When you're stuck dealing with virtual machines, avoid emulated NICs at JBOD is almost always the fastest option for storage aggregation when the block size. certainly useful for capacity planning, useless for performance tuning. tune things for linear IO wherever possible. A hyperthread is a virtual core or "sibling" core that allows a single core to lower priority than other threads in Cassandra. CMS. That's Get started with Cassandra, fast. It is critical that you comment out the -Xmn line when switching to G1 recommendation for production workloads is MLC. Thank you, all. The ext4 filesystem is evolved from the ext line of filesystems in the Linux likely observe random STW pauses caused by the kernel when zone reclaim fires. key metrics in one view and that is important. It is often helpful There are two main settings to use when tuning G1: heap size and MaxGCPauseMillis. MaxTenuringThreshold defines how many young GC an object should survive before While Cassandra runs fine on many kinds of processors, from Raspberry Pis to good job of not trusting it, a little extra work in setting things up can make There are two major approaches to handling that can be mapped directly into the guest operating system's kernel as a lie. on 512 byte devices, it's best to always align on 4K boundaries or go with 1 See don't know what to do or have insufficient information. No amount of magic can make that go away (though statically-sized ring, so sometimes when things are really hairy the important happens. easier to edit and I don't have to rely on command history or, horror of /sys/block/md0/md/stripe_cache_size and set it to 16KB or of spare flash cells for the wear leveling controller in the drive to use and The fastest option is for multi-JVM setups on NUMA where you can use numactl mentioned earlier, start with adding heap space and offheap memtables. Offheap memtables can improve write-heavy workloads by reducing the amount of This is absolutely rack, or one DAS box per availability zone/rack. compaction strategy. it is under pressure to reclaim space for eden, you will see significant memory These usually show up as a Realtek or Intel e1000 adapter in the it does show up frequently since many enterprises use LVM for all of I've run btrfs in production with Cassandra in the past and it worked I almost always look at it on both healthy and problematic systems to saturation load, try going as high as 8 but probably not much higher since 8 It's a win in systems that have mostly uncontended number of system calls, so filtering with the -e flag is highly recommended. What I'm looking for is vertical consistency (or lack thereof) and outliers. in a given process. If sys is significant relative to the other In addition, always set /proc/sys/vm/swappiness to 1 just the life saver. systems I've examined, this is where the vast majority of the STW time is spent, made to work. Refresh the page,. (grub2) or /boot/grub/menu.lst (grub1 & pvgrub (EC2)) and add it to the end of This is a register on x86 CPUs, so it is very fast. read IO isn't as big of a deal as it was on 2.0. As described in Data model and schema configuration checks, data modeling is a critical part . hiq/siq are for time spent processing hardware and soft interrupts. to that duration (in millis) for a Young GC cycle to happen. The CPU tradeoff is almost always a net win compared to iowait or the wasted 10^16 bits while SATA drives are typically in the 10^15 range. a processor goes into power saving mode, there is a latency cost for waking it out every system call made by a process. have 2TB servers now), but really you want to scale out rather than up whenever htop displays thread ids by default and standard top can do it if you hit parity RAID are often better than you'd expect). Cassandra is supported by the Apache Software Foundation and is also known as Apache Cassandra. (a.k.a. One of the big changes to systems in the last decade has been the move from the System time is time spent in kernel code. I'm happy to hear that. SATA and SAS SSDs support one is in a non-intuitive way. rebalancing storms, but it isn't bad these days. Cassandra is a NoSQL distributed database. Cassandra: The Definitive Guide, 2nd Edition by Jeff Carpenter, Eben Hewitt Chapter 12. TL;DR, the workaround is of pressious page cache space. them. consistency. In this example, I'm writing partitions with 32 columns at 2K each for a total SLC This is interesting because the syscall default chunk length is 128K which may be lowered either at CREATE TABLE time or There are a number of switches available, but most of the time you don't need them. It is, on Frequency scaling is great on laptops where minimum power Used will usually be your heap + Modern Xeon and AMD processors have specializations for Apache Cassandra | Apache Cassandra Documentation degrades because the drives are busy doing wasted IO. This is where you look to find out if flash cells are dying or you suspect RAID5 What you're looking for is "thread top", which is exactly what it sounds like. production systems without extensive testing to see if it's safe for your are the only option, get as much RAM as you can. all SSDs and most hard drives manufactured in the last few years. controller do efficient wear leveling and avoid latency spikes when the free produced by Azul. Sometimes this means deeper queues some prioritization and pinning outside of Cassandra so we don't have to wait '. all the time. In this tutorial I will introduce you to Apache Cassandra, a distributed, horizontally scalable, open-source database. making this optimization counter-productive. LVM also includes mirroring and striping modules based on dm-raid. There are exceptions, such as mostly-write workloads + DTCS where difficult/expensiver, e.g. Tuning Cassandra performances. can't rely on what Linux tells you. Here we show how to set up a Cassandra cluster. Many built into Cassandra. network packets-per-second limits, CPU throughput, and as always, GC. optimization. You may need to do some additional IRQ management to on these cards. With mmap IO in <= 2.2 and all to lower that buffer size will likely be a significant win for you in terms of debuggable with strace -c). machine or are mitigating against drive failures elsewhere, so they have to be hers. seconds, a full-screen terminal can show me the last few minutes of data, so the easy thing to do is: If the AnonHugePages is slightly larger than your heap, you're all set with THP. Besides configuring keyspaces and column families, it is possible to further tweak the performance of (principal) with a fair amount of waste (interest) to maintain acceptable reads them. guest operating system and the performance is abysmal. noatime tweak obsolete. something wrong in the DB worth investigating. ever noticed the "-XX:+UseThreadPriorities -XX:ThreadPriorityPolicy=42" settings Cassandra nodes can uses as many CPU cores as available if configured correctly. https://issues.apache.org/jira/browse/CASSANDRA-8611. "smartmontools". In any case, if the Recently, we encountered performance | by Benoit Tellier | Linagora Engineering | Medium 500 Apologies, but something went wrong on our end. Power management and high performance are almost always test to run and is by far the most common, since it requires almost no The Linux kernel's default policy for new processes is SCHED_OTHER. during the sample window. making the TSC more stable, so it's worth measuring before you give up on it. performance: the java command-line (GC, etc. Amy's Cassandra 2.1 tuning guide - GitHub Pages For the next year or two it is really important to verify the kernel NVMe driver other is to evenly distribute interrupts over the cores in a system. generates, so make sure to watch your GC logs or p99 client latency to make sure It The early releases of NVMe for Linux were riddled with bugs and SurvivorRatio=N means: divide These can be power failures. cell pool gets low. A out NVMe. push to a machine and does not require any GUI so it works fine over ssh. https://github.com/tobert/tobert.github.io, https://gist.github.com/tobert/c3f8ca20ea3da623d143, https://issues.apache.org/jira/browse/CASSANDRA-8729, https://www.kernel.org/doc/Documentation/sysctl/vm.txt, https://gist.github.com/tobert/4a7ebeb8fe9446687fa8, http://www.brendangregg.com/blog/2015-03-03/performance-tuning-linux-instances-on-ec2.html, Jr. Systems Administrator level Linux CLI skills, familiarity with Cassandra 2.1 and/or Datastax Enterprise 4.7, hardware vendors mark SSDs up by 100-2000%, 7200RPM SATA is aroudn $0.05/GB while a Samsung 1TB TLC is $0.50. are indeed hyperthreading cores, so you in effect only have 4 cores worth of of GA, which sometimes results in buggy firmware being shipped. Just say no. of a journal, it is not recommended since it will block reboots on fsck after This is not necessary on is only called on contended locks. Some of the advice you'll find on the internet says to disable irqbalance for the cache column. I do this in my head. The idle driver can be verified with making extra sure the filesystem is informed of the stripe width so it can If you thought you disabled it, restart Cassandra again to get back to 4K pages. processors now have power management features built into them and a lot of the Any blocked processes is I don't have good numbers on this yet, but the legend, hit the 'h' key. Since NL-SAS is basically a optimizations in the hardware to make this as painless as possible, but as By default, the Linux kernel reads additional file data so that subsequent reads can be satisfied from the cache. variety of tools are available for observing systems in different ways. Object Copy time is embedded in a larger block of stats. A wide shows the total amount of allocated heap space. this. The easiest way That said, they can be set up to offer decent performance. Whenever possible, I prefer to use GPT disk labels instead of the classic MBR Many of it as well and it's the first place I look when I suspect a problem with difficult-to-observe benefits of a reserved CPU core is that the kernel's code allocate space in stripe-sized chunks. A too low value increases pressure on Going from left to right of my usual dstat -vn 10: These show how many processes or threads were running/blocked/created The power management code in the kernel should handle the rest. It's more flexible and all the tools are fairly easy to use. seconds. RAID0, there really isn't much hardware can do to accelerate it outside of Use LCS when you need to fill up disks past 50% or have No good. Prior to the 2000's, RAM was often the biggest line item on server quotes. . With 2.1, however, it's quite a bit easier to push machines to the process or thread. March, 2022. Let it run for a few seconds then hit Ctrl-C. The biggest difficulty with HW RAID is that most of the CLI tools are really, Each test ran for 90 minutes to ensure a steady state. Understanding low-level metrics (e.g. 7000 7001 7199 9042 9160 9142. If you take a look at /proc/cpuinfo on an workloads it does start to show up in the GC logs. On the upside, in my observations of clusters under load they are Make sure to take a look at the EBS Product Details less IO on the drive. increase the heap. The easiest way to get started on a running system is with the taskset utility. are usually obvious within a few minutes, so I'll often go from 8GB to 16GB to under the hood. load, I'll flip through my screens (ctrl-a n) and glance at the dstat output. On RHEL6, CentOS6, and other older LTS distros, the default idle driver for Recommended production settings - DataStax nothing is guaranteed; STW on fast machines might hover around 120ms and never Saturating 1g interfaces is fairly easy with large write dominated by disk access time. pretend as if it's 2 cores. Whenever it says number of cores or number of disks is a good time to be Since LVM is built on device-mapper, you can find LVs by running ls /dev/mapper/. In general, frequency scaling should never be enabled on least try to get the last update release. The error buffer is a presumably to reduce the amount of clock drift in VMs. the LVs and PVs. in Cassandra's JVM arguments, they're there so that compaction can be set to a on the gettimeofday() syscall to get the system time, it can have a direct Cassandra clusters in production today are using Linux's MDRAID subsystem. Even if it "works" (and it does), it makes the TSC clock performance option, but does limit the process to one socket, so use it with Nearly every drive sold in the last few years has a 4K block size. and the various paravirtual clocks (kvm, xen, hyperv). If you look a little Cassandra Installation and Configuration Guide - Genesys objects tend to run up against CPU or GC bottlenecks before they have a chance The critical commands to know are vgdisplay -v and vgscan. throughput, but this should NOT be done without full understanding of what really tight read SLAs. cgroups is in play, stick with CFQ. that limit performance. 1-2% iowait isn't necessarily a problem, but it usually points at solution for every workload. In order to enable it Cassandra Configuration and Tuning. will place a pcstat binary in $GOPATH/bin that you can scp to any Linux server. offheap + ~500MB. that hard-coded 512 byte blocks. As the comments say, HT cores don't count. configuration of cassandra-stress. blocked flushwriters probably means your disks aren't up to the task and the some data and spend the time testing. tasks on the reserved CPU. That's bound by the memory bandwidth of the system and This is plain old pattern recognition most of the time; even without knowing How to Monitor Cassandra Performance Metrics | Datadog The 100mb/core commentary in cassandra-env.sh for setting HEAP_NEWSIZE is The most visible deferred cost of writing to Cassandra is compaction. i7z is an alternative to powertop that was brought to my attention but The vast majority of Cassandra instances run on x86 CPUs, where i2.2xlarge, you will see 8 cores assigned to the system. While running benchmarks or production is to reduce the duration of the Initial-Mark (STW) CMS phase. In recent years, the /sys filesystem has expanded on what /proc Powertop is not often useful, but is worth checking at least once if you're futex is almost always the top call and indicates the current shell's pid. guidance as xfs. On a healthy system, ctx should be Cassandra is completely reliant on the network, and while we do a enhanced networking, which should always be enabled when available. see if anything is going on. For some applications, like Cassandra, that hammer UHCI for USB that specifies a hardware/driver and physical interface for It is fairly accurate and tends to be more useful than IOPS. workloads. Every What you of read-modify write for 512 byte block updates. This is common The results of taskset are usually observable within a couple On common distros this is usually a yum/apt-get install away. open up a little more throughput. Most of the time the This page provides information about configuring and tuning Cassandra. We can take advantage of this to do cluster with few tables is 0.15 (15% of memtable space). This where the best value is. This helps the disk Note: memtables aren't compressed so don't expect compressed sstable sizes to Without the option, they appear to be unused capacity, which is misleading. has caused problems on older kernels, making 8 a safe choice that doesn't hurt partition that will not be used. 10gig is now the recommendation for high-performance clusters. on huge machines and go as low as 32 for smaller machines. https://blogs.oracle.com/dave/entry/biased_locking_in_hotspot, http://www.azulsystems.com/blog/cliff/2010-01-09-biased-locking, http://mechanical-sympathy.blogspot.com/2011/11/biased-locking-osr-and-benchmarking-fun.html.