Work with your system designers and developers to plan for disk
storage requirements in testing and production database systems. Work with host
system administrators to determine where to place your disk store directories
on each peer computer.
Consider these guidelines when designing disk stores:
- Tables can be overflowed,
persisted, or both. For efficiency, place table data that is overflowed on one
disk store with a dedicated physical disk. Place table data that is persisted,
or persisted and overflowed, on another disk store with on a different physical
For example, gateway sender, AsyncEventListener, and
DBSynchronizer queues are always overflowed and may be persisted. Assign them
to overflow disk stores if you do not persist, and to persistence disk stores
if you do. Ensure that each disk store resides on a separate physical disk, for
- When calculating your disk
requirements, consider your table modification patterns and compaction
strategy. GemFire XD creates each oplog file at the specified MAXLOGSIZE. Obsolete
DML operations are only removed from the oplogs during compaction, so you need
enough space to store all operations that are done between compactions. For
tables where you are doing a mix of updates and deletes, if you use automatic
compaction, a good upper bound for the required disk space is
(1 / (1 - (compaction_threshold/100)) ) * data size
where data size is the total size of all the table data you store
in the disk store. So, for the default COMPACTIONTHRESHOLD of 50, the disk
space is roughly twice your data size. The compaction thread could lag behind
other operations, causing disk use to rise above the threshold temporarily. If
you disable automatic compaction, the amount of disk required depends on how
many obsolete operations accumulate between manual compactions.
- Based on your anticipated
disk storage requirements and the available disks on your host systems:
- Make sure the new
storage does not interfere with other processes that use disk on your systems.
If possible, store your files to disks that are not used by other processes,
including virtual memory or swap space. If you have multiple disks available,
for the best performance, place one directory on each disk.
- Use different
directories for different peers that run on the same computer. You can use any
number of directories for a single disk store.
- Choose disk store names
that reflect how the stores should be used and that work for your operating
systems. Disk store names are used in the disk file names:
- Use disk store names
that satisfy the file naming requirements for your operating system. For
example, if you store your data to disk in a Windows system, your disk store
names could not contain any of these reserved characters, < > : " / \ | ?
- Do not use very long
disk store names. The full file names must fit within your operating system
limits. On Linux, for example, the standard limitation is 255 characters.
- Create each disk store with CREATE DISKSTORE before you create
persistent or overflow tables.
- You may choose to parallelize disk access for oplog and overflow files using
by targeting disk store files to multiple logical disk partitions.
- GemFire XD disk store files must be highly available. Back up disk store files
on a regular schedule, either by copying the files while the system is
offline, or by using the backup command to perform online backups.
GemFire XD peers in the cluster manage their local disk stores using the
properties you specify in the
After you create named disk stores, you can create tables that persist
or overflow their data to disk stores.