1# SPDX-License-Identifier: GPL-2.0
2#
3# DRBD device driver configuration
4#
5
6comment "DRBD disabled because PROC_FS or INET not selected"
7	depends on PROC_FS='n' || INET='n'
8
9config BLK_DEV_DRBD
10	tristate "DRBD Distributed Replicated Block Device support"
11	depends on PROC_FS && INET
12	select LRU_CACHE
13	select LIBCRC32C
14	default n
15	help
16
17	  NOTE: In order to authenticate connections you have to select
18	  CRYPTO_HMAC and a hash function as well.
19
20	  DRBD is a shared-nothing, synchronously replicated block device. It
21	  is designed to serve as a building block for high availability
22	  clusters and in this context, is a "drop-in" replacement for shared
23	  storage. Simplistically, you could see it as a network RAID 1.
24
25	  Each minor device has a role, which can be 'primary' or 'secondary'.
26	  On the node with the primary device the application is supposed to
27	  run and to access the device (/dev/drbdX). Every write is sent to
28	  the local 'lower level block device' and, across the network, to the
29	  node with the device in 'secondary' state.  The secondary device
30	  simply writes the data to its lower level block device.
31
32	  DRBD can also be used in dual-Primary mode (device writable on both
33	  nodes), which means it can exhibit shared disk semantics in a
34	  shared-nothing cluster.  Needless to say, on top of dual-Primary
35	  DRBD utilizing a cluster file system is necessary to maintain for
36	  cache coherency.
37
38	  For automatic failover you need a cluster manager (e.g. heartbeat).
39	  See also: http://www.drbd.org/, http://www.linux-ha.org
40
41	  If unsure, say N.
42
43config DRBD_FAULT_INJECTION
44	bool "DRBD fault injection"
45	depends on BLK_DEV_DRBD
46	help
47
48	  Say Y here if you want to simulate IO errors, in order to test DRBD's
49	  behavior.
50
51	  The actual simulation of IO errors is done by writing 3 values to
52	  /sys/module/drbd/parameters/
53
54	  enable_faults: bitmask of...
55	  1	meta data write
56	  2               read
57	  4	resync data write
58	  8	            read
59	  16	data write
60	  32	data read
61	  64	read ahead
62	  128	kmalloc of bitmap
63	  256	allocation of peer_requests
64	  512	insert data corruption on receiving side
65
66	  fault_devs: bitmask of minor numbers
67	  fault_rate: frequency in percent
68
69	  Example: Simulate data write errors on /dev/drbd0 with a probability of 5%.
70		echo 16 > /sys/module/drbd/parameters/enable_faults
71		echo 1 > /sys/module/drbd/parameters/fault_devs
72		echo 5 > /sys/module/drbd/parameters/fault_rate
73
74	  If unsure, say N.
75