# # DRBD device driver configuration # comment "DRBD disabled because PROC_FS or INET not selected" depends on PROC_FS='n' || INET='n' config BLK_DEV_DRBD tristate "DRBD Distributed Replicated Block Device support" depends on PROC_FS && INET select LRU_CACHE select LIBCRC32C default n help NOTE: In order to authenticate connections you have to select CRYPTO_HMAC and a hash function as well. DRBD is a shared-nothing, synchronously replicated block device. It is designed to serve as a building block for high availability clusters and in this context, is a "drop-in" replacement for shared storage. Simplistically, you could see it as a network RAID 1. Each minor device has a role, which can be 'primary' or 'secondary'. On the node with the primary device the application is supposed to run and to access the device (/dev/drbdX). Every write is sent to the local 'lower level block device' and, across the network, to the node with the device in 'secondary' state. The secondary device simply writes the data to its lower level block device. DRBD can also be used in dual-Primary mode (device writable on both nodes), which means it can exhibit shared disk semantics in a shared-nothing cluster. Needless to say, on top of dual-Primary DRBD utilizing a cluster file system is necessary to maintain for cache coherency. For automatic failover you need a cluster manager (e.g. heartbeat). See also: http://www.drbd.org/, http://www.linux-ha.org If unsure, say N. config DRBD_FAULT_INJECTION bool "DRBD fault injection" depends on BLK_DEV_DRBD help Say Y here if you want to simulate IO errors, in order to test DRBD's behavior. The actual simulation of IO errors is done by writing 3 values to /sys/module/drbd/parameters/ enable_faults: bitmask of... 1 meta data write 2 read 4 resync data write 8 read 16 data write 32 data read 64 read ahead 128 kmalloc of bitmap 256 allocation of peer_requests 512 insert data corruption on receiving side fault_devs: bitmask of minor numbers fault_rate: frequency in percent Example: Simulate data write errors on /dev/drbd0 with a probability of 5%. echo 16 > /sys/module/drbd/parameters/enable_faults echo 1 > /sys/module/drbd/parameters/fault_devs echo 5 > /sys/module/drbd/parameters/fault_rate If unsure, say N.