0001 # SPDX-License-Identifier: GPL-2.0
0002 #
0003 # DRBD device driver configuration
0004 #
0005
0006 comment "DRBD disabled because PROC_FS or INET not selected"
0007 depends on PROC_FS='n' || INET='n'
0008
0009 config BLK_DEV_DRBD
0010 tristate "DRBD Distributed Replicated Block Device support"
0011 depends on PROC_FS && INET
0012 select LRU_CACHE
0013 select LIBCRC32C
0014 help
0015
0016 NOTE: In order to authenticate connections you have to select
0017 CRYPTO_HMAC and a hash function as well.
0018
0019 DRBD is a shared-nothing, synchronously replicated block device. It
0020 is designed to serve as a building block for high availability
0021 clusters and in this context, is a "drop-in" replacement for shared
0022 storage. Simplistically, you could see it as a network RAID 1.
0023
0024 Each minor device has a role, which can be 'primary' or 'secondary'.
0025 On the node with the primary device the application is supposed to
0026 run and to access the device (/dev/drbdX). Every write is sent to
0027 the local 'lower level block device' and, across the network, to the
0028 node with the device in 'secondary' state. The secondary device
0029 simply writes the data to its lower level block device.
0030
0031 DRBD can also be used in dual-Primary mode (device writable on both
0032 nodes), which means it can exhibit shared disk semantics in a
0033 shared-nothing cluster. Needless to say, on top of dual-Primary
0034 DRBD utilizing a cluster file system is necessary to maintain for
0035 cache coherency.
0036
0037 For automatic failover you need a cluster manager (e.g. heartbeat).
0038 See also: https://www.drbd.org/, http://www.linux-ha.org
0039
0040 If unsure, say N.
0041
0042 config DRBD_FAULT_INJECTION
0043 bool "DRBD fault injection"
0044 depends on BLK_DEV_DRBD
0045 help
0046
0047 Say Y here if you want to simulate IO errors, in order to test DRBD's
0048 behavior.
0049
0050 The actual simulation of IO errors is done by writing 3 values to
0051 /sys/module/drbd/parameters/
0052
0053 enable_faults: bitmask of...
0054 1 meta data write
0055 2 read
0056 4 resync data write
0057 8 read
0058 16 data write
0059 32 data read
0060 64 read ahead
0061 128 kmalloc of bitmap
0062 256 allocation of peer_requests
0063 512 insert data corruption on receiving side
0064
0065 fault_devs: bitmask of minor numbers
0066 fault_rate: frequency in percent
0067
0068 Example: Simulate data write errors on /dev/drbd0 with a probability of 5%.
0069 echo 16 > /sys/module/drbd/parameters/enable_faults
0070 echo 1 > /sys/module/drbd/parameters/fault_devs
0071 echo 5 > /sys/module/drbd/parameters/fault_rate
0072
0073 If unsure, say N.
