Whether you are considering DRBD® as a data replication solution to achieve high-availability or disaster recovery in your deployments, or you are seasoned in its use already, there are some hardware and environment requirements that you should consider.
Memory Requirements and Maximum Device Size
DRBD can replicate block devices in real-time or asynchronously, depending on your needs. You can use it in embedded devices to replicate mere KiBs of block storage with a scant memory footprint, or scale it up to many TiBs, which will require several MiBs of memory. You will need about 32MiB of RAM per 1TiB of storage.
DRBD’s maximum device size is 1PiB (1024TiB).
CPU Architecture Requirements
LINBIT® currently tests DRBD 9, DRBD’s latest major version, to build on the following CPU architectures:
Recent versions of DRBD 9 are only tested to build on 64 bit CPU architecture. Building DRBD on 32 bit CPU architecture is unsupported and may or may not work.
Minimum Linux Kernel Version
The minimum Linux kernel version supported in DRBD 9.0 is 2.6.32. Starting with DRBD 9.1, the minimum Linux kernel version supported is 3.10.
Maximum Number of DRBD Volumes on a Node
Because of the 20 bit constraint on minor numbers, the maximum number of DRBD volumes that you can have on a node is 1048576.
Maximum Number of Volumes per DRBD Resource
The maximum number of volumes per DRBD resource is 65535.
Maximum Number of Nodes Accessing a Resource
There is a limit of 32 nodes that can access the same DRBD resource concurrently. In practice, clusters of more than five nodes are not recommended.
You can find this information, along with more details about calculating DRBD’s memory requirements more precisely, in the DRBD 9 User’s Guide.
Also, let us know about your experiences if you one day deploy or have to support a 32-node storage cluster.