hi, Thank you for your answers, starting with the most important point from your answers I understand that
"it is OK to go more than 1 TB in disk usage" so in this case if I am going to use the 50% of the disk capacity I will end up having around 3 TB per node which in this case I will not need to use a docker solution which is a very good usa case for us. The goal of my setup is to save large data volumes in every node (~ 3 TB - 50% usage of HD) with the current hardware that we possess. The high availability I consider it standard since we are going to have 2 DCs with RF3. I also have to note that Datastax also recommends usage no more than 500 GB - 1 TB. Cheers, Vasilis Sent with [ProtonMail](https://protonmail.com) Secure Email. ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Thursday, April 18, 2019 6:56 PM, Jacques-Henri Berthemet <jacques-henri.berthe...@genesys.com> wrote: > So how much data can you safely fit per node using SSDs with Cassandra 3.11? > How much free space do you need on your disks? > > There should be some recommendations on node sizes on: > > http://cassandra.apache.org/doc/latest/operating/hardware.html > > [Documentation - Apache > Cassandra](http://cassandra.apache.org/doc/latest/operating/hardware.html) > cassandra.apache.org > The Apache Cassandra database is the right choice when you need scalability > and high availability without compromising performance. Linear scalability > and proven fault-tolerance on commodity hardware or cloud infrastructure make > it the perfect platform for mission-critical data. Cassandra's support for > replicating across multiple datacenters is best-in-class, providing lower > latency for your ... > > --------------------------------------------------------------- > > From: Jon Haddad <j...@jonhaddad.com> > Sent: Thursday, April 18, 2019 6:43:15 PM > To: user@cassandra.apache.org > Subject: Re: [EXTERNAL] multiple Cassandra instances per server, possible? > > Agreed with Jeff here. The whole "community recommends no more than > 1TB" has been around, and inaccurate, for a long time. > > The biggest issue with dense nodes is how long it takes to replace > them. 4.0 should help with that under certain circumstances. > > On Thu, Apr 18, 2019 at 6:57 AM Jeff Jirsa <jji...@gmail.com> wrote: >> >> Agreed that you can go larger than 1T on ssd >> >> You can do this safely with both instances in the same cluster if you >> guarantee two replicas aren’t on the same machine. Cassandra provides a >> primitive to do this - rack awareness through the network topology snitch. >> >> The limitation (until 4.0) is that you’ll need two IPs per machine as both >> instances have to run in the same port. >> >> >> -- >> Jeff Jirsa >> >> >> On Apr 18, 2019, at 6:45 AM, Durity, Sean R <sean_r_dur...@homedepot.com> >> wrote: >> >> What is the data problem that you are trying to solve with Cassandra? Is it >> high availability? Low latency queries? Large data volumes? High concurrent >> users? I would design the solution to fit the problem(s) you are solving. >> >> >> >> For example, if high availability is the goal, I would be very cautious >> about 2 nodes/machine. If you need the full amount of the disk – you *can* >> have larger nodes than 1 TB. I agree that administration tasks (like >> adding/removing nodes, etc.) are more painful with large nodes – but not >> impossible. For large amounts of data, I like nodes that have about 2.5 – 3 >> TB of usable SSD disk. >> >> >> >> It is possible that your nodes might be under-utilized, especially at first. >> But if the hardware is already available, you have to use what you have. >> >> >> >> We have done multiple nodes on single physical hardware, but they were two >> separate clusters (for the same application). In that case, we had a >> different install location and different ports for one of the clusters. >> >> >> >> Sean Durity >> >> >> >> From: William R <tri...@protonmail.com.INVALID> >> Sent: Thursday, April 18, 2019 9:14 AM >> To: user@cassandra.apache.org >> Subject: [EXTERNAL] multiple Cassandra instances per server, possible? >> >> >> >> Hi all, >> >> >> >> In our small company we have 10 nodes of (2 x 3 TB HD) 6 TB each, 128 GB ram >> and 64 cores and we are thinking to use them as Cassandra nodes. From what I >> am reading around, the community recommends that every node should not keep >> more than 1 TB data so in this case I am wondering if it is possible to >> install 2 instances per node using docker so each docker instance can write >> to its own physical disk and utilise more efficiently the rest hardware (CPU >> & RAM). >> >> >> >> I understand with this setup there is the danger of creating a single point >> of failure for 2 Cassandra nodes but except that do you think that is a >> possible setup to start with the cluster? >> >> >> >> Except the docker solution do you recommend any other way to split the >> physical node to 2 instances? (VMWare? or even maybe 2 separate >> installations of Cassandra? ) >> >> >> >> Eventually we are aiming in a cluster consisted of 2 DCs with 10 nodes each >> (5 baremetal nodes with 2 Cassandra instances) >> >> >> >> Probably later when we will start introducing more nodes to the cluster we >> can decommissioning the "double-instaned" ones and aim for a more >> homogeneous solution.. >> >> >> >> Thank you, >> >> >> >> Wil >> >> >> ________________________________ >> >> The information in this Internet Email is confidential and may be legally >> privileged. It is intended solely for the addressee. Access to this Email by >> anyone else is unauthorized. If you are not the intended recipient, any >> disclosure, copying, distribution or any action taken or omitted to be taken >> in reliance on it, is prohibited and may be unlawful. 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