The overflow feature uses disk stores as an extension of the in-memory cache.
Persistence uses disk stores to store a redundant copy of the data.
These two options can be used individually or together.
Disk storage is available for these cached data types:
- Cached regions. Persist
and/or overflow data from your cached data regions.
- Server’s client subscription
queues. Overflow the messaging queues to control memory use.
- Gateway sender queues.
Persist these for high availability. These queues always overflow.
- PDX serialization metadata.
Persist metadata about objects you serialize using GemFire PDX
Each member has its own set of disk stores, completely separate from the disk stores
of any other member. For each disk store, you define where and how the data is
stored to disk. You can store data from multiple regions and queues in a single disk
This figure shows a member with disk stores D through R defined. The member has two
persistent regions using disk store D and an overflow region and an overflow queue
using disk store R.
What GemFire Writes to the Disk Store
The following list describes the items that GemFire writes the disk store:
- List of members that host the store
and information on their status, such as running or offline and time stamps.
- List of regions in the disk store.
For cached regions, these are the names you give the regions. For all other
data, these are GemFire internal region names.
- For each region:
- Region configuration
attributes pertaining to loading and capacity management, used to
load the data quickly on startup.
- Region data operations.
GemFire does not write indexes to disk.
Disk Store State
Disk store access and management differs according to whether the store is online or
While a member is running, its disk stores are online in the GemFire system. When the
member closes its cache and exits, its disk stores go offline. When the member
starts up again, its disk stores come back online.