Relational Database Server¶
As in any computer system, CPU, RAM memory, disk storage, and network speed are important components of performance. The relational database component of DataJoint is no exception to this rule. This section discusses the various factors relating to selecting a server for your DataJoint pipelines.
CPU speed and parallelism (number of cores/threads) will impact the speed of queries and the number of simultaneous queries which can be efficiently supported by the system. It is a good rule of thumb to have enough cores to support the number of active users and background tasks you expect to have running during a typical ‘busy’ day of usage. For example, a team of 10 people might want to have 8 cores to support a few active queries and background tasks.
The amount of RAM will impact the amount of DataJoint data kept in memory, allowing for faster querying of data since the data can be searched and returned to the user without needing to access the slower disk drives. It is a good idea to get enough memory to fully store the more important and frequently accessed portions of your dataset with room to spare, especially if in-database blob storage is used instead of external bulk storage.
The disk storage for a DataJoint database server should have fast random access, ideally with flash-based storage to eliminate the rotational delay of mechanical hard drives.
When network connections are used, network speed and latency are important to ensure that large query results can be quickly transferred across the network and that delays due to data entry/query round-trip have minimal impact on the runtime of the program.
DataJoint datasets can consist of many thousands or even millions of records. Generally speaking one would want to make sure that the relational database system has sufficient CPU speed and parallelism to support a typical number of concurrent users and to execute searches quickly. The system should have enough RAM to store the primary key values of commonly used tables and operating system caches. Disk storage should be fast enough to support quick loading of and searching through the data. Lastly, network bandwidth must be sufficient to support transferring user records quickly.
Database replication may be beneficial if system downtime or precise database responsiveness is a concern Replication can allow for easier coordination of maintenance activities, faster recovery in the event of system problems, and distribution of the database workload across server machines to increase throughput and responsiveness.
Master/slave replication allows for creation of a read-only database copy which is updated in real time. This copy can be used for backup or queries which are not time sensitive. It can also be upgraded with read-write usage in the event that the main database fails.
Multi-master replication configurations allow for all replicas to be used in a read/write fashion, with the workload being distributed among all machines. However, multi-master replication is also more complicated, requiring front-end machines to distribute the workload, similar performance characteristics on all replicas to prevent bottlenecks, and redundant network connections to ensure the replicated machines are always in sync.
It is usually best to go with the simplest solution which can suit the requirements of the installation, adjusting workloads where possible and adding complexity only as needs dictate.
Resource requirements of course depend on the data collection and processing needs of the given pipeline, but there are general size guidelines that can inform any system configuration decisions. A reasonably powerful workstation or small server should support the needs of a small group (2-10 users). A medium or large server should support the needs of a larger user community (10-30 users). A replicated or distributed setup of 2 or more medium or large servers may be required in larger cases. These requirements can be reduced through the use of external or cloud storage, which is discussed in the subsequent section.
|Usage Scenario||DataJoint Database Computer||Hardware Recommendation|
|Single User||Personal Laptop or Workstation||4 Cores, 8-16GB or more of RAM, SSD or better storage|
|Small Group (e.g. 2-10 Users)||Workstation or Small Server||8 or more Cores, 16GB or more of RAM, SSD or better storage|
|Medium Group (e.g. 10-30 Users)||Small to Medium Server||8-16 or more Cores, 32GB or more of RAM, SSD/RAID or better storage|
|Large Group/Department (e.g. 30-50+ Users)||Medium/Large Server or Multi-Server Replication||16-32 or more Cores, 64GB or more of RAM, SSD Raid storage, multiple machines|
|Multi-Location Collaboration (30+ users, Geographically Distributed)||Large Server, Advanced Replication||16-32 or more Cores, 64GB or more of RAM, SSD Raid storage, multiple machines; potentially multiple machines in multiple locations|