1# 2# DRBD device driver configuration 3# 4 5comment "DRBD disabled because PROC_FS, INET or CONNECTOR not selected" 6 depends on PROC_FS='n' || INET='n' || CONNECTOR='n' 7 8config BLK_DEV_DRBD 9 tristate "DRBD Distributed Replicated Block Device support" 10 depends on PROC_FS && INET && CONNECTOR 11 select LRU_CACHE 12 default n 13 help 14 15 NOTE: In order to authenticate connections you have to select 16 CRYPTO_HMAC and a hash function as well. 17 18 DRBD is a shared-nothing, synchronously replicated block device. It 19 is designed to serve as a building block for high availability 20 clusters and in this context, is a "drop-in" replacement for shared 21 storage. Simplistically, you could see it as a network RAID 1. 22 23 Each minor device has a role, which can be 'primary' or 'secondary'. 24 On the node with the primary device the application is supposed to 25 run and to access the device (/dev/drbdX). Every write is sent to 26 the local 'lower level block device' and, across the network, to the 27 node with the device in 'secondary' state. The secondary device 28 simply writes the data to its lower level block device. 29 30 DRBD can also be used in dual-Primary mode (device writable on both 31 nodes), which means it can exhibit shared disk semantics in a 32 shared-nothing cluster. Needless to say, on top of dual-Primary 33 DRBD utilizing a cluster file system is necessary to maintain for 34 cache coherency. 35 36 For automatic failover you need a cluster manager (e.g. heartbeat). 37 See also: http://www.drbd.org/, http://www.linux-ha.org 38 39 If unsure, say N. 40 41config DRBD_FAULT_INJECTION 42 bool "DRBD fault injection" 43 depends on BLK_DEV_DRBD 44 help 45 46 Say Y here if you want to simulate IO errors, in order to test DRBD's 47 behavior. 48 49 The actual simulation of IO errors is done by writing 3 values to 50 /sys/module/drbd/parameters/ 51 52 enable_faults: bitmask of... 53 1 meta data write 54 2 read 55 4 resync data write 56 8 read 57 16 data write 58 32 data read 59 64 read ahead 60 128 kmalloc of bitmap 61 256 allocation of EE (epoch_entries) 62 63 fault_devs: bitmask of minor numbers 64 fault_rate: frequency in percent 65 66 Example: Simulate data write errors on /dev/drbd0 with a probability of 5%. 67 echo 16 > /sys/module/drbd/parameters/enable_faults 68 echo 1 > /sys/module/drbd/parameters/fault_devs 69 echo 5 > /sys/module/drbd/parameters/fault_rate 70 71 If unsure, say N. 72