# SPDX-License-Identifier: GPL-2.0-only## 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 CRC32	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: https://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.