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	help
15
16	  NOTE: In order to authenticate connections you have to select
17	  CRYPTO_HMAC and a hash function as well.
18
19	  DRBD is a shared-nothing, synchronously replicated block device. It
20	  is designed to serve as a building block for high availability
21	  clusters and in this context, is a "drop-in" replacement for shared
22	  storage. Simplistically, you could see it as a network RAID 1.
23
24	  Each minor device has a role, which can be 'primary' or 'secondary'.
25	  On the node with the primary device the application is supposed to
26	  run and to access the device (/dev/drbdX). Every write is sent to
27	  the local 'lower level block device' and, across the network, to the
28	  node with the device in 'secondary' state.  The secondary device
29	  simply writes the data to its lower level block device.
30
31	  DRBD can also be used in dual-Primary mode (device writable on both
32	  nodes), which means it can exhibit shared disk semantics in a
33	  shared-nothing cluster.  Needless to say, on top of dual-Primary
34	  DRBD utilizing a cluster file system is necessary to maintain for
35	  cache coherency.
36
37	  For automatic failover you need a cluster manager (e.g. heartbeat).
38	  See also: https://www.drbd.org/, http://www.linux-ha.org
39
40	  If unsure, say N.
41
42config DRBD_FAULT_INJECTION
43	bool "DRBD fault injection"
44	depends on BLK_DEV_DRBD
45	help
46
47	  Say Y here if you want to simulate IO errors, in order to test DRBD's
48	  behavior.
49
50	  The actual simulation of IO errors is done by writing 3 values to
51	  /sys/module/drbd/parameters/
52
53	  enable_faults: bitmask of...
54	  1	meta data write
55	  2               read
56	  4	resync data write
57	  8	            read
58	  16	data write
59	  32	data read
60	  64	read ahead
61	  128	kmalloc of bitmap
62	  256	allocation of peer_requests
63	  512	insert data corruption on receiving side
64
65	  fault_devs: bitmask of minor numbers
66	  fault_rate: frequency in percent
67
68	  Example: Simulate data write errors on /dev/drbd0 with a probability of 5%.
69		echo 16 > /sys/module/drbd/parameters/enable_faults
70		echo 1 > /sys/module/drbd/parameters/fault_devs
71		echo 5 > /sys/module/drbd/parameters/fault_rate
72
73	  If unsure, say N.
74