Multitenancy

Guides

1. What is multitenancy? | Multitenant architecture | Cloudflare

In cloud computing, multitenancy means that multiple customers of a cloud vendor are using the same computing resources. Despite the fact that they share resources, cloud customers aren't aware of each other, and their data is kept totally separate.

2. IaaS vs. PaaS vs. SaaS | Redhat

3. Database Multi-Tenancy For SaaS | lighttag

There are three multi-tenancy models: Database, Schema, and Table.

1. Database multi-tenancy (Shared Hardware / IaaS)

• In an exemplary implementation, the application has no concept of tenants.

• Tenant databases only share the server hardware resources.
• A virtual machine (VM) created host each tenant’s database.
• Each tenant is assigned its own VM and an exclusive database process that serves the tenant’s database.
• Predominantly used in Infrastructure-as-a-Service (IaaS) cloud providers such as Amazon web services (ec2)
• Disadvantage
  • Increased overhead due to redundant components
  • lack of coordination using limited machine resources in a non-optimal way.
  • The co-located database processes make un-coordinated accesses to the disk.
• Advantage
  • multi-tenancy can be supported without any changes in database layer.

2. Schema/Container multi-tenancy (Shared Process / PaaS)

• Application connects to a database once and has some logic to choosing which schema to connect to when serving a particular tenant.

• Tenants share resources within a single database process running at each server.
• This multi-tenancy model is typically observed on PaaS cloud providers such as Microsoft SQL Azure, Google Megastore, etc.
• Advantage
  • More effective sharing of some of the critical physical resources such as I/O and main memory
  • ensuring a level of isolation of user data in separate tables.
• Disadvantages
  • Does not support the notion of elasticity that would allow dynamic migration of databases hosted at one DBMS instance to another DBMS.
  • DBMSs become sluggish when a large number of tenant databases are hosted especially when workload spikes.

3. Table multi-tenancy (Shared Table / SaaS)

Multi tenancy | ClickHouse Docs

• every row in every table is associated with a given tenant.

• In the shared table model, the tenants’ data are stored in a shared table called the heap table.
• To support flexibility in schema and data types across the different tenants, the heap table does not contain the tenant’s schema or column information.
• Disadvantage
  • Requires that all tenants reside on the same database engine and release
  • Limits specialized database functionality, such as spatial or object based, and requires that all tenants use a limited subset of functionality.
• Advantage
  • This multi-tenancy model is ideal when multiple tenants have similar schema and access patterns with minimal customizations, thus providing effective sharing of resources.
  • Such similarity is observed in SaaS where a generic application tenant is customized to meet specific customer requirements.