The application of DRBD in Linux-HA

Haibo Zhang4/28/2014

What is DRBD?

• DRBD (Distributed Replicated Block Device) is a software development for high availability clusters

What is the HA?

• The Linux-HA (High-Availability Linux project provides a high availability (clustering) Solution for Linux, FreeBSD, OpenBSD, Solaris and which promotes reliability, availability, and serviceability (RAS).

Easy way to understand

• Disk Array• RAID （ Redundant Arrays of Inexpensive Disks ， RAID）

The structure of HA

The structure of HA

• DRBD core functionality by Linux kernel implements, Under the file system it is closest to the IO stack.

• Conducive to the transmission of the data• System should be the shared disk file system like GFS2 ； OCFS2

How the DRBD running

• Mirroring of important data• Fully synchronous• switch between master slave

File transfer

The local write return immediately successfuland the data is sent to the other party, dual both power-down, the data may be lost

Local and the other write successfully identified and returned. Dual power-down or also damaged disk, the data may be lost

Return immediately write local success, the data on buffer. may be lost

Copydata

Asynchronous

Memory

synchronization

synchronization

heartbeat

Split brain

• Each node want to switch to master node when the net broken • Quorum Algorithm to handle split brain

Core of the progress

Inputdata

heartbeat

Copydata

Receive Data

respond

Transfer data to node

Inputdata

heartbeat Copydata

DRBD in the in reality

• Company with big data• Bank • Database system

Tha

Thank You!