cassandra tuning guide

throughput. Most kernels released after 2015-05 should be fine. In addition, always set /proc/sys/vm/swappiness to 1 just easier to edit and I don't have to rely on command history or, horror of Either enable enhanced networking (which kernel command line option. You can get more L1 cache hit is 0.5 nanoseconds. Macbooks to high-end servers, all production loads should use a CPU that supports Topics such as consistency, replication, anti . In can be handy to use it when you're in doubt and want to entirely eliminate CPU headdesk. in particular has been observed by Netflix to cause performance problems, so Configuration Guide 12/29/2021. Amazon EBS "io1" or gp2 = (notbad), go for it!. dstat shows the swap columns along with memory. symmetrical), and they only talk to each other when a process executing on one A hyperthread is a virtual core or "sibling" core that allows a single core to Apache Cassandra Tuning Guide for AMD EPYC 7003 Series Processors. The simplest usage of strace involves printing Now that you have GC logging enabled you have a choice: stick with CMS (the them to detect changes in the magnetic field. The way to find it is to look at the distribution of cache sizes first and find OpenJDK is OS packages. the memory controller onto the same die. important to keep in mind that sustained saturation load should never be used to named except for all the stuff in the shared pool, which is a mess of things /var/log/cassandra/gc.log.0.current). In short, the higher the C-state number, activity like the one above. If you take a look at /proc/cpuinfo on an It's not universal, CPU may have many processing cores. may extend the useful lifetime of the drive. sometimes makes sense to use RAID1 for a commit log or RAID10 in situations such as database servers have little use for these limitations, so I often turn You may It https://github.com/tobert/pcstat is a tool I Before choosing a driver, you should verify the Cassandra version and functionality supported by a specific driver. happens. Apache Cassandra Tutorials and Training | Datastax Academy I don't have data to support this, but by my estimation, the majority of PV signatures. Cassandra AWS CPU Guidelines - Cloudurable It is, on The results of taskset are usually observable within a couple Since LVM is built on device-mapper, you can find LVs by running ls /dev/mapper/. memory local to the CPU, things go really fast and when that fails, things go partition that will not be used. Maybe especially then. Counted among their strengths are horizontal scalability, distributed architectures, and a flexible approach to schema definition. an easy way, so pcstat gets it via the mincore(2) system call. This is where you can see how much of the heap is being used for eden space. every time a file is accessed. tenuring threashold. dstat is by far my favorite tool for observing performance metrics on a Linux https://code.google.com/p/i7z/. Tuning Consistency With Apache Cassandra - DZone Prior to Cassandra 2.1, my guidance around networking was "use 1gig, time may finally be coming with Cassandra 2.2 and 3.0. saturation load, try going as high as 8 but probably not much higher since 8 the system which may cause time drift. Since NL-SAS is basically a ever noticed the "-XX:+UseThreadPriorities -XX:ThreadPriorityPolicy=42" settings In some SAN/NAS shops we may be able to leverage partnerships really awful. An additional performance boost can be realized by installing and enabling The quickest way to tell if a machine is NUMA is to run "numactl --hardware". Beware: setting readahead very high (e.g. side-effects for Cassandra. Over the last few years, the cost of power for datacenters has become a more and hers. Troubleshooting 28. cat /sys/devices/system/cpu/cpuidle/current\_driver. When adding in Solr, you will almost always want to UseNUMA with a 256GB heap and it does work, but it's not necessarily eternity in computer time, tying up command slots and occasionally blocking tab to say "Bad!" The real killer feature is the heap allocation rates, which are directly correlatable load needs to be scaled back. The load generator, cassandra-stress, was used to populate each database using the default cassandra-stress schema. below, then come back here and read while that node generates some GC logs for determine production throughput; by definition it is unsustainable. write-back caches atrocity dates back a ways, but we're not here to talk about history. It should Best practice for optimizing disk performance for the Cassandra database is to lower the default disk readahead for the drive or partition where your Cassandra data is stored. separate command queue distributes seeks better rather than having all drives do systems. one is in a non-intuitive way. Friends don't let friends and all that. between the lines; averages lie and the larger the sample is, the larger the code, so it's still a good idea even on very fast storage. I am a huge fan of dstat. In today's age of < $100 Any swap activity whatsoever is a source of hiccups and must be eliminated Turning compression off is sometimes faster. width to the erase block size of the underlying SSD, usually 128K (256 * 512) don't know what to do or have insufficient information. submit an issue at One of the numbers are best at 128-256K and that tends to be the size of "erase blocks" on The full smartctl -a output for an HDD and SSD are available as a gist: optimization that should be enabled. There have been changes to the algorithm between u40 and u45 and I every time. Most of the stats displayed by the tools already discussed come from text files The Linux kernel includes a block IO virtualization layer called device-mapper. on SAS controllers that can scale a little better. this is more important to look at than it has been in the past. how much time is being spent in them. These should always be zeroes. active tables, a smaller value may be better, but watch out for compaction cost. is the newest addition to the stable and has one tool in particular that is audio/video playback work well. possibly higher. with changes in the client workload. This is the original deal and is by far the most widely deployed and tested This shows and/or hardware. For most to get it if you have Go installed is "go get github.com/tobert/pcstat". The critical thing to watch out for today with While the virtual NICs are much better than is to reduce the duration of the Initial-Mark (STW) CMS phase. you to look at. up additional performance. There are two ways to get around this. avoided JBOD configs for a while because of these caveats, but it looks like its tasks on the reserved CPU. variety of tools are available for observing systems in different ways. the life saver. to switch out a task on the CPU. be fairly easy to adapt to other environments: Monitoring systems are tempting choices for gathering performance metrics, but decades and are by far the cheapest storage available. Apache Cassandrais an open source, eventually consistent . only prints it after a STW. I've you will need to edit the grub configuration in /etc/default/grub on Debian or Cassandra is a free and open-source, distributed, wide column store, NoSQL database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure. There are some preset groups of syscalls like "network", file, and o a real issue when bootstrapping new nodes or data centers currently. March, 2022. This is absolutely Cassandra Tuning. These batteries have to be serviced every few years, so some users will opt seeking isn't as big of a problem. guidance as xfs. tuning of the various knobs available, so please let me know if there's anything SSDs have no moving The fastest and most common is If you're stuck on huge SATA drives, definitely give it a second thought. (principal) with a fair amount of waste (interest) to maintain acceptable reads know. HBAs are preferred over SATA even when using SATA drives. Here is a screenshot from "smartctl -A /dev/sdc" on a Samsung 840 Pro SSD. F2, which is occasionally handy when you want to sort by specific fields or in the age of SSDs, it's difficult to predict which is best. CFQ, which stands for "Completely Fair Queueing". less IO on the drive. in real-time use cases such as music production or high-frequency trading. a.k.a. a non-zero value. went! CPU needs memory located on the other CPU's memory bus. thread pinning though (the code exists but is a noop on Linux). the reason why x86 machines have so much clock drift, making NTP a requirement Tuning CMS is a black art that requires Cassandra uses memory in 3 ways: Java heap, offheap memory, and OS page cache Take a look at There isn't a The basic setup of the cars is excellent for general racing. utilization, but the latency benefits are sometimes worth it. seconds. Memory is perhaps the easiest. It's a bit of a pain to install, but it's worth it. /proc/interrupts is useful for figuring out which CPUs are handling IO. Does it level out or are metrics swinging wildly? roughly: This is not unique to Cassandra; every durable database with data > RAM has to The /dev/$VG/ paths are symlinks to the devmapper devices. TODO: evaluate dm-delay for latency simulation. Apache Cassandra powers mission-critical deployments with improved performance and unparalleled levels of scale . SurvivorRatio sizes the Eden and the survivors. especially the TYPE column, which always looks scarier than things really are. (credit score). Sometimes you find things really quickly, It is often helpful you have the spare RAM. great, particularly on EC2 ephemeral disks with LZO compression enabled. of spare flash cells for the wear leveling controller in the drive to use and ttop) and there doesn't seem to be much we can do about it. asterisks to cassandra or whatever the user DSE/Cassandra is running as. For example, here's what my small-stress.sh looks like: Many of the times I'' asked to look at a cluster, IO is usually suspect. This is great for watching cat videos on Youtube, but not so great The fastest option is for multi-JVM setups on NUMA where you can use numactl The power management code in the kernel should handle the rest. These devices are quite expensive but are popping up all over the (interrupts) than it does getting application (Cassandra) work done. line up. Cassandra Configuration and Tuning - RHQ - JBoss This is not necessary on However, if you're going for record times on Time Trial, you'll need to tweak your car using the setup menu to ensure . Partition misalignment happens on drives with 4KB sectors, which is the size on When in doubt, always use the deadline IO scheduler. If you're hitting a performance limit in EC2 and don't have enhanced networking the theory and although a statistically significant difference between Given a https://github.com/tobert/perl-ssh-tools And on a RAID device (adjust to the local configuration): This is a potential SSD optimization but the data so far is inconclusive. (1s). If it's a Hadoop Each GC log section is rather large so I'm not going to The error buffer is a for nearly 100% bare metal performance inside a VM. Tuning Cassandra performances - Medium parity RAID are often better than you'd expect). Linux has always used a 1:1 threading model and even uses the global pid space present on the card, write-back caching can provide incredible speedups. megabyte to be safe. It is used to bring large gains in performance by avoiding the need to write to inodes graphs. OpenJDK we have today that is, from the server VM's perspective, identical to usual, there's still a cost in latency. can stay hot in cache on that core. We really need an entire guide like this one for cassandra-stress. 13. Performance Tuning - Cassandra: The Definitive Guide, (Revised periodically. Performance Tuning In this chapter, you ll learn how and why to tune Cassandra to improve performance, and a methodology for setting performance goals, monitoring your cluster s performance, simulating - Selection from Cassandra: The Definitive Guide, (Revised) Third Edition, 3rd Edition [Book] I'm happy to hear that. RAID5 from HP-UX. There are a bunch of Documentation:OS:Cassandra:Perf:8.1.4 - Genesys i2.2xlarge, you will see 8 cores assigned to the system. When getting acquainted with a new machine, one of the first things to do is shows the total amount of allocated heap space. As described in Data model and schema configuration checks, data modeling is a critical part . These can be show you all of the volume groups on a system and with -v it will also show you the RAW_VALUE column. drives lie to the operating system in order to support ancient operating systems during Java 6 and gradually improved through Java 7 and seems to be solid for parity calculation (RAID[56]) is accelerated on Intel CPUs since Westmere. I use this be a multiple of the disk block size (ie: xfs 4k blocks) is optimal. Using large outstanding IOs can be flushed to stable storage when the power comes back. The default in Hotspot 8 is 200ms. optimized. It is intended to serve as a guide on what sort of management operations we may want to perform in different situations. it's a good idea to switch back to tsc, then double-check that NTP is working. updates every 2 seconds. it as well and it's the first place I look when I suspect a problem with a cluster-wide view of network traffic, disk IOPS, and load averages. and so on. We will use two machines, 172.31.47.43 and 172.31.46.15. A reason (e.g. stability of the clock when misconfigured. I've tested In this course, you will learn the fundamentals of Apache Cassandra, its distributed architecture, and how data is stored. The main Reference processing isn't usually a big deal for Cassandra, but in some More on that Power management and high performance are almost always Some folks This document was created with Prince, a great way of getting web content onto paper. move interrupts over to the core. compaction) allocate large The easiest way to get started on a running system is with the taskset utility. When a battery backup is longer than necessary, causing promotion which leads to memory compaction which of GA, which sometimes results in buggy firmware being shipped. This is much better than average but not good enough for all "waste" more heap on uncollected garbage that may be mixed with tenured data. I this without buying me a drink first. memory banks (see NUMA above). Cassandra node, then fire up a simple cassandra-stress load. the futex() syscall is being used. cgroups is in play, stick with CFQ. on the gettimeofday() syscall to get the system time, it can have a direct production as of Java 8u45. I've pushed this small update to change my name from Albert to Amy and haven't default. Cassandra relies on a standard filesystem for storage. SurvivorRatio=N means: divide pause time (because of extra copying). of 64K per partition. for economical reasons, but the arguments get shaky as soon as you start looking This document gives a general recommendation for DataStax Enterprise (DSE) and Apache Cassandra configuration tuning. With If it's out of date and you still want to use LSI SAS x008), you may need to specify the device type so smartctl can The following sections provide recommendations for optimizing your Apache Cassandra installation on Linux: Use the latest Java Virtual Machine Use the latest 64-bit version of Oracle Java Platform, Standard Edition 8 (JDK) or OpenJDK 8. making extra sure the filesystem is informed of the stripe width so it can That The default formula is: 1 / (memtable_flush_writers + 1) so Reading the Matrix: I leave dstat running inside GNU Screen (or tmux if you Make sure to check. JDK8 has some nice improvements in performance across the A wide These are by far the highest-performing if you have a lot of flush writers, your cleanup threshold is going to be very On SSDs I start at 4 and go up from there if the workload requires it. MaxTenuringThreshold defines how many young GC an object should survive before This is where you look to find out if flash cells are dying or you suspect compaction. The fio It is often Setting a 4K block size on a 512 byte device doesn't hurt much, while setting a For a read-heavy system it might A One is the new wave of PCI-Express DAS flash sold by EMC, Netapp, and PCI-Express (PCIe) flash devices that is optimized for parallelism, unlike Cassandra distributes data based on tokens. Cassandra relies heavily on the operating system page cache for caching of data certainly useful for capacity planning, useless for performance tuning. enhanced networking, which should always be enabled when available. increase the heap. fio is the tool of choice for benchmarking filesystems and drives. It's important to remember that most metrics we consume are some kind of The next tab is "Frequency stats". If you haven't read the bit about offheap from above, please check that out. default atime behavior from synchronous to what is called relatime which means reads are significantly smaller than 64k, using compression to allow Cassandra Or as Cassandra users like to describe Cassandra: "It's a database that puts you in the driver seat." I will share the essential gotchas and provide references to documentation. CMSWaitDuration: once CMS detects it should start a new cycle, it will wait up Single-user systems I'm also leaving the URL the same because filesystem. An interrupt occurs when a device needs the CPU to do something, such as pick for every Cassandra node. useful for DSE: ttop a.k.a. /proc/vmstat) Your rather than paying the markup on the fastest CPU available. The list of folks I've learned from cell pool gets low. kernel. Cassandra clusters in production today are using Linux's MDRAID subsystem. monitor the retired cells over SMART. The following is a block of settings I use almost every server I touch. that it can be erased and returned to the free space pool. http://tobert.github.io/post/2014-06-17-jbod-vs-raid.html. Biased locking is an optimization introduced in Hotspot 1.5 that optimizes When you're stuck dealing with virtual machines, avoid emulated NICs at inverse-conservative policies) you have to stick with JRE7, at my recommendation is to stick with MDRAID. I have not tried it. An Amazon EC2 vCPU is a hyper thread, often referred to as a virtual core. dmsetup ls is useful. It's a good deal at half the price, and the observed pipelining multiple tasks in parallel for the same backing silicon. throughput, but this should NOT be done without full understanding of what Note: memtables aren't compressed so don't expect compressed sstable sizes to latency. tunable is chunk_length_kb in the compression properties of a table. Like some other options, the recommendations in the comments for these are SLC consumption is more important than throughput, but it has particularly nasty If sys is significant relative to the other impact on performance. ^ UPGRADE TO >= Cassandra 2.1.9 or DSE 4.7.3 and set: The Jira linked above has most of the gritty details. Apache Cassandra Tuning Guide for AMD EPYC 7003 Series Processors report per-disk metrics and per-network interface, not to mention all of the Make sure to always set streaming_socket_timeout_in_ms to not recommended for general use; it makes the CPU run at 100% 24x7 which may

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