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https://github.com/schoebel/mars
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401 lines
12 KiB
Plaintext
401 lines
12 KiB
Plaintext
#
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# MARS configuration
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#
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config MARS
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tristate "block storage replication MARS"
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depends on m
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depends on BLOCK && PROC_SYSCTL && HIGH_RES_TIMERS
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default n
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---help---
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See https://github.com/schoebel/mars/docu/
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Only compile as a module!
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config MARS_CHECKS
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bool "enable simple runtime checks in MARS"
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depends on MARS
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default y
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---help---
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These checks should be rather lightweight. Use them
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for beta testing and for production systems where
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safety is more important than performance.
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In case of bugs in the reference counting, an automatic repair
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is attempted, which lowers the risk of memory corruptions.
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Disable only if you need the absolutely last grain of
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performance.
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If unsure, say Y here.
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config MARS_DEBUG
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bool "enable full runtime checks and some tracing in MARS"
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depends on MARS
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default n
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---help---
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Some of these checks and some additional error tracing may
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consume noticable amounts of memory.
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OFF for production systems. ON for testing!
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config MARS_DEBUG_DEFAULT
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bool "turn on debug messages by default (may flood the logfiles)"
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depends on MARS_DEBUG
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default n
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---help---
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normally OFF
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config MARS_DEBUG_MEM
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bool "debug memory operations"
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depends on MARS_DEBUG
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default n
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---help---
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This adds considerable space and time overhead, but catches
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many errors (including some that are not caught by kmemleak).
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Use only for development and thorough testing!
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config MARS_DEBUG_MEM_STRONG
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bool "intensified debugging of memory operations"
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depends on MARS_DEBUG_MEM
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default y
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---help---
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Trace all block allocations, find more errors.
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Adds some overhead.
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Use for debugging of new bricks or for intensified
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regression testing.
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config MARS_DEBUG_ORDER0
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bool "also debug order0 operations"
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depends on MARS_DEBUG_MEM
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default n
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---help---
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Turn even order 0 allocations into order 1 ones and provoke
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heavy memory fragmentation problems from the buddy allocator,
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but catch some additional memory problems.
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Use only if you know what you are doing!
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Normally OFF.
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config MARS_DEFAULT_PORT
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int "port number where MARS is listening"
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depends on MARS
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default 7777
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---help---
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Best practice is to uniformly use the same port number
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in a cluster. Therefore, this is a compiletime constant.
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You may override this at insmod time via the mars_port= parameter.
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config MARS_SEPARATE_PORTS
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bool "use separate port numbers for traffic shaping"
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depends on MARS
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default y
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---help---
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When enabled, the following port assignments will be used:
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CONFIG_MARS_DEFAULT_PORT : updates of symlinks
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CONFIG_MARS_DEFAULT_PORT + 1 : replication of logfiles
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CONFIG_MARS_DEFAULT_PORT + 2 : (initial) sync traffic
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As a consequence, external traffic shaping may be used to
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individually control the network speed for different types
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of traffic.
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Please don't hinder the symlink updates in any way -- they are
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most vital, and they produce no mass traffic at all
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(it's only some kind of meta-information traffic).
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Say Y if you have a big datacenter.
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Say N if you cannot afford a bigger hole in your firefall.
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If unsure, say Y.
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config MARS_IPv4_TOS
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bool "use TOS / DSCP in IPv4"
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depends on MARS_SEPARATE_PORTS
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default y
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---help---
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Tag IP traffic differently for different ports.
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In certain private networks, this can improve certain
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network bottlenecks.
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config MARS_MEM_RETRY
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bool "make MARS memory allocation more robust"
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depends on MARS
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default y
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---help---
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Normally ON. Switch only off for systems having very low memory.
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config MARS_LOGDIR
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string "absolute path to the logging directory"
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depends on MARS
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default "/mars"
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---help---
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Path to the directory where all MARS messages will reside.
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Usually this is equal to the global /mars directory.
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Logfiles and status files obey the following naming conventions:
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0.debug.log
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1.info.log
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2.warn.log
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3.error.log
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4.fatal.log
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5.total.log
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Logfiles must already exist in order to be appended.
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Logiles can be rotated by renaming them and creating
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a new empty file in place of the old one.
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Status files follow the same rules, but .log is replaced
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by .status, and they are created automatically. Their content
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is however limited to a few seconds or minutes.
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config MARS_ROLLOVER_INTERVAL
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int "rollover time of logging status files (in seconds)"
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depends on MARS
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default 3
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---help---
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May influence the system load; dont use too low nubmers.
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config MARS_SCAN_INTERVAL
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int "re-scanning of symlinks in /mars/ (in seconds)"
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depends on MARS
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default 5
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---help---
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May influence the system load; dont use too low nubmers.
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config MARS_PROPAGATE_INTERVAL
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int "network propagation delay of changes in /mars/ (in seconds)"
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depends on MARS
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default 5
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---help---
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May influence the system load; dont use too low nubmers.
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config MARS_SYNC_FLIP_INTERVAL
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int "interrpt sync by logfile update after (seconds)"
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depends on MARS
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default 60
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---help---
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0 = OFF. Normally ON.
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When disabled, application of logfiles may wait for
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a very time, until full sync has finished. As a
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consequence, your /mars/ filesystem may run out
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of space. When enabled, the applied logfiles can
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be deleted, freeing space on /mars/. Therefore,
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will usually want this. However, you may increase
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the time interval to increase throughput in favour
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of latency.
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config MARS_NETIO_TIMEOUT
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int "timeout for remote IO operations (in seconds)"
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depends on MARS
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default 30
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---help---
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In case of network hangs, don't wait forever, but rather
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abort with -ENOTCONN
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when == 0, wait forever (may lead to hanging operations
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similar to NFS hard mounts)
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config MARS_MEM_PREALLOC
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bool "avoid memory fragmentation by preallocation"
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depends on MARS
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default y
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---help---
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Normally ON. Switch off only for EXPERIMENTS!
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config MARS_FAST_FULLSYNC
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bool "decrease network traffic at initial sync"
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depends on MARS
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default y
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---help---
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Normally ON.
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When on, both sides will read the data, compute a md5
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checksum, and compare them. Only in case the checksum
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mismatches, the data will be actually transferred over
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the network. This may increase the IO traffic in favour
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of network traffic. Usually it does no harm to re-read
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the same data twice (only in case of mismatches) over bio
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because RAID controllers will usually cache their data
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for some time. In case of buffered aio reads from filesystems,
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the data is cached by the kernel anyway.
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config MARS_SHOW_CONNECTIONS
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bool "show connection status symlinks"
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depends on MARS
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default n
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---help---
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Normally OFF.
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When enabled, the status of all current network connections is
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written to /mars/resource-$resource/local-$host/connect-*
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showing the current status of all network connections by
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the following encoding:
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-1 = connection is closed (not intended to start)
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0 = connection is interrupted / not established
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1 = connection is established at TCP level
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Warning! the symlinks are not deleted by the kernel. You have
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to cleanup old symlinks by yourself in userspace.
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When you forget the cleanup in regular intervals, you may
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end up with thoundands of symlinks accumulating in the
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/mars/resource-$resource/local-$host/ directory over a
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longer time.
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If unsure, say N here.
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config MARS_LOGROT
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bool "allow logrotate during operation"
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depends on MARS
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default y
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---help---
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Normally ON. Switch off only for EXPERIMENTS!
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config MARS_MIN_SPACE_4
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int "absolutely necessary free space in /mars/ (hard limit in GB)"
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depends on MARS
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default 2
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---help---
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HARDEST EMERGENCY LIMIT
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When free space in /mars/ drops under this limit,
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transaction logging to /mars/ will stop at all,
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even at all primary resources. All IO will directly go to the
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underlying raw devices. The transaction logfile sequence numbers
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will be disrupted, deliberately leaving holes in the sequence.
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This is a last-resort desperate action of the kernel.
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As a consequence, all secodaries will have no chance to
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replay at that gap, even if they got the logfiles.
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The secondaries will stop at the gap, left in an outdated,
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but logically consistent state.
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After the problem has been fixed, the secondaries must
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start a full-sync in order to continue replication at the
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recent state.
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This is the hardest measure the kernel can take in order
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to TRY to continue undisrupted operation at the primary side.
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In general, you should avoid such situations at the admin level.
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Please implement your own monitoring at the admin level, which warns
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you and/or takes appropriate countermeasures much earlier.
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Never rely on this emergency feature!
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config MARS_MIN_SPACE_3
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int "free space in /mars/ for primary logfiles (additional limit in GB)"
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depends on MARS
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default 2
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---help---
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MEDIUM EMERGENCY LIMIT
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When free space in /mars/ drops under
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MARS_MIN_SPACE_4 + MARS_MIN_SPACE_3,
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elder transaction logfiles will be deleted at primary resources.
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As a consequence, the secondaries may no longer be able to
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get a consecute series of copies of logfiles.
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As a result, they may get stuck somewhere inbetween at an
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outdated, but logically consistent state.
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This is a desperate action of the kernel.
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After the problem has been fixed, some secondaries may need to
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start a full-sync in order to continue replication at the
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recent state.
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In general, you should avoid such situations at the admin level.
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Please implement your own monitoring at the admin level, which warns
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you and/or takes appropriate countermeasures much earlier.
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Never rely on this emergency feature!
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config MARS_MIN_SPACE_2
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int "free space in /mars/ for secondary logfiles (additional limit in GB)"
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depends on MARS
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default 2
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---help---
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MEDIUM EMERGENCY LIMIT
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When free space in /mars/ drops under
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MARS_MIN_SPACE_4 + MARS_MIN_SPACE_3 + MARS_MIN_SPACE_2,
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elder transaction logfiles will be deleted at secondary resources.
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As a consequence, some local secondary resources
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may get stuck somewhere inbetween at an
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outdated, but logically consistent state.
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This is a desperate action of the kernel.
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After the problem has been fixed and the free space becomes
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larger than MARS_MIN_SPACE_4 + MARS_MIN_SPACE_3 + MARS_MIN_SPACE_2
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+ MARS_MIN_SPACE_2, the secondary tries to fetch the missing
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logfiles from the primary again.
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However, if the necessary logfiles have been deleted at the
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primary side in the meantime, this may fail.
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In general, you should avoid such situations at the admin level.
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Please implement your own monitoring at the admin level, which warns
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you and/or takes appropriate countermeasures much earlier.
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Never rely on this emergency feature!
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config MARS_MIN_SPACE_1
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int "free space in /mars/ for replication (additional limit in GB)"
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depends on MARS
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default 2
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---help---
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LOWEST EMERGENCY LIMIT
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When free space in /mars/ drops under MARS_MIN_SPACE_4
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+ MARS_MIN_SPACE_3 + MARS_MIN_SPACE_2 + MARS_MIN_SPACE_1,
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fetching of transaction logfiles will stop at local secondary
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resources.
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As a consequence, some local secondary resources
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may get stuck somewhere inbetween at an
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outdated, but logically consistent state.
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This is a desperate action of the kernel.
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After the problem has been fixed and the free space becomes
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larger than MARS_MIN_SPACE_4 + MARS_MIN_SPACE_3 + MARS_MIN_SPACE_2
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+ MARS_MIN_SPACE_2, the secondary will continue fetching its
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copy of logfiles from the primary side.
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In general, you should avoid such situations at the admin level.
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Please implement your own monitoring at the admin level, which warns
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you and/or takes appropriate countermeasures much earlier.
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Never rely on this emergency feature!
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config MARS_MIN_SPACE_0
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int "total space needed in /mars/ for (additional limit in GB)"
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depends on MARS
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default 12
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---help---
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Operational pre-requirement.
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In order to use MARS, the total space available in /mars/ must
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be at least MARS_MIN_SPACE_4 + MARS_MIN_SPACE_3 + MARS_MIN_SPACE_2
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+ MARS_MIN_SPACE_1 + MARS_MIN_SPACE_0.
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If you cannot afford that amount of storage space, please use
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DRBD in place of MARS.
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config MARS_LOGROT_AUTO
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int "automatic logrotate when logfile exceeds size (in GB)"
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depends on MARS_LOGROT
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default 32
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---help---
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You could switch this off by setting to 0. However, deletion
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of really huge logfiles can take several minutes, or even substantial
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fractions of hours (depending on the underlying filesystem).
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Thus it is highly recommended to limit the logfile size to some
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reasonable maximum size. Switch only off for experiments!
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config MARS_PREFER_SIO
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bool "prefer sio bricks instead of aio"
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depends on MARS
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default n
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---help---
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Normally OFF for production systems.
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Only use as alternative for testing.
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