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434 lines
10 KiB
Groff
434 lines
10 KiB
Groff
.\" Man page generated from reStructuredText.
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.TH "CRUSHTOOL" "8" "January 12, 2014" "dev" "Ceph"
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.SH NAME
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crushtool \- CRUSH map manipulation tool
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.SH SYNOPSIS
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.nf
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\fBcrushtool\fP ( \-d \fImap\fP | \-c \fImap.txt\fP | \-\-build \-\-num_osds \fInumosds\fP
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\fIlayer1\fP \fI\&...\fP | \-\-test ) [ \-o \fIoutfile\fP ]
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.fi
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.sp
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.SH DESCRIPTION
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.INDENT 0.0
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.TP
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.B \fBcrushtool\fP is a utility that lets you create, compile, decompile
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and test CRUSH map files.
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.UNINDENT
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.sp
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CRUSH is a pseudo\-random data distribution algorithm that efficiently
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maps input values (typically data objects) across a heterogeneous,
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hierarchically structured device map. The algorithm was originally
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described in detail in the following paper (although it has evolved
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some since then):
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.INDENT 0.0
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.INDENT 3.5
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\fI\%http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf\fP
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.UNINDENT
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.UNINDENT
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.sp
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The tool has four modes of operation.
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.INDENT 0.0
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.TP
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.B \-\-compile|\-c map.txt
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will compile a plaintext map.txt into a binary map file.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-decompile|\-d map
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will take the compiled map and decompile it into a plaintext source
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file, suitable for editing.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-build \-\-num_osds {num\-osds} layer1 ...
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will create map with the given layer structure. See below for a
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detailed explanation.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-test
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will perform a dry run of a CRUSH mapping for a range of input
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object names. See below for a detailed explanation.
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.UNINDENT
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.sp
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Unlike other Ceph tools, \fBcrushtool\fP does not accept generic options
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such as \fB\-\-debug\-crush\fP from the command line. They can however be
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provided via the CEPH_ARGS environment variable. For instance, to
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silence all output from the CRUSH subsystem:
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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CEPH_ARGS="\-\-debug\-crush 0" crushtool ...
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.SH RUNNING TESTS WITH --TEST
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.sp
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The test mode will use the input crush map ( as specified with \fB\-i
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map\fP ) and perform a dry run of CRUSH mapping or random placement (
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if \fB\-\-simulate\fP is set ). On completion, two kinds of reports can be
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created. The \fB\-\-show\-...\fP options output human readable informations
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on stderr. The \fB\-\-output\-csv\fP option creates CSV files that are
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documented by the \fB\-\-help\-output\fP option.
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.INDENT 0.0
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.TP
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.B \-\-show\-statistics
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for each rule display the mapping of each object. For instance:
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.INDENT 7.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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CRUSH rule 1 x 24 [11,6]
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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shows that object \fB24\fP is mapped to devices \fB[11,6]\fP by rule
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\fB1\fP\&. At the end of the mapping details, a summary of the
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distribution is displayed. For instance:
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.INDENT 7.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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rule 1 (metadata) num_rep 5 result size == 5: 1024/1024
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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shows that rule \fB1\fP which is named \fBmetadata\fP successfully
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mapped \fB1024\fP objects to \fBresult size == 5\fP devices when trying
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to map them to \fBnum_rep 5\fP replicas. When it fails to provide the
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required mapping, presumably because the number of \fBtries\fP must
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be increased, a breakdown of the failures is displays. For instance:
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.INDENT 7.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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rule 1 (metadata) num_rep 10 result size == 8: 4/1024
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rule 1 (metadata) num_rep 10 result size == 9: 93/1024
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rule 1 (metadata) num_rep 10 result size == 10: 927/1024
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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shows that although \fBnum_rep 10\fP replicas were required, \fB4\fP
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out of \fB1024\fP objects ( \fB4/1024\fP ) were mapped to \fBresult size
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== 8\fP devices only.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-show\-bad\-mappings
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display which object failed to be mapped to the required number of
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devices. For instance:
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.INDENT 7.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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bad mapping rule 1 x 781 num_rep 7 result [8,10,2,11,6,9]
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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shows that when rule \fB1\fP was required to map \fB7\fP devices, it
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could only map six : \fB[8,10,2,11,6,9]\fP\&.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-show\-utilization
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display the expected and actual utilisation for each device, for
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each number of replicas. For instance:
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.INDENT 7.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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device 0: stored : 951 expected : 853.333
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device 1: stored : 963 expected : 853.333
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\&...
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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shows that device \fB0\fP stored \fB951\fP objects and was expected to store \fB853\fP\&.
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Implies \fB\-\-show\-statistics\fP\&.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-show\-utilization\-all
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displays the same as \fB\-\-show\-utilization\fP but does not suppress
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output when the weight of a device is zero.
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Implies \fB\-\-show\-statistics\fP\&.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-show\-choose\-tries
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display how many attempts were needed to find a device mapping.
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For instance:
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.INDENT 7.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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0: 95224
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1: 3745
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2: 2225
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\&..
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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shows that \fB95224\fP mappings succeeded without retries, \fB3745\fP
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mappings succeeded with one attempts, etc. There are as many rows
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as the value of the \fB\-\-set\-choose\-total\-tries\fP option.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-output\-csv
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create CSV files (in the current directory) containing information
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documented by \fB\-\-help\-output\fP\&. The files are named after the rule
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used when collecting the statistics. For instance, if the rule
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metadata is used, the CSV files will be:
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.INDENT 7.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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metadata\-absolute_weights.csv
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metadata\-device_utilization.csv
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\&...
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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The first line of the file shortly explains the column layout. For
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instance:
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.INDENT 7.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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metadata\-absolute_weights.csv
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Device ID, Absolute Weight
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0,1
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\&...
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-output\-name NAME
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prepend \fBNAME\fP to the file names generated when \fB\-\-output\-csv\fP
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is specified. For instance \fB\-\-output\-name FOO\fP will create
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files:
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.INDENT 7.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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FOO\-metadata\-absolute_weights.csv
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FOO\-metadata\-device_utilization.csv
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\&...
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.UNINDENT
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.sp
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The \fB\-\-set\-...\fP options can be used to modify the tunables of the
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input crush map. The input crush map is modified in
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memory. For example:
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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$ crushtool \-i mymap \-\-test \-\-show\-bad\-mappings
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bad mapping rule 1 x 781 num_rep 7 result [8,10,2,11,6,9]
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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could be fixed by increasing the \fBchoose\-total\-tries\fP as follows:
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.INDENT 0.0
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.INDENT 3.5
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.INDENT 0.0
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.TP
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.B $ crushtool \-i mymap \-\-test
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\-\-show\-bad\-mappings \-\-set\-choose\-total\-tries 500
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.UNINDENT
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.UNINDENT
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.UNINDENT
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.SH BUILDING A MAP WITH --BUILD
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.sp
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The build mode will generate hierarchical maps. The first argument
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specifies the number of devices (leaves) in the CRUSH hierarchy. Each
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layer describes how the layer (or devices) preceding it should be
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grouped.
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.sp
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Each layer consists of:
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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bucket ( uniform | list | tree | straw ) size
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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The \fBbucket\fP is the type of the buckets in the layer
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(e.g. "rack"). Each bucket name will be built by appending a unique
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number to the \fBbucket\fP string (e.g. "rack0", "rack1"...).
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.sp
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The second component is the type of bucket: \fBstraw\fP should be used
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most of the time.
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.sp
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The third component is the maximum size of the bucket. A size of zero
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means a bucket of infinite capacity.
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.SH EXAMPLE
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.sp
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Suppose we have two rows with two racks each and 20 nodes per rack. Suppose
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each node contains 4 storage devices for Ceph OSD Daemons. This configuration
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allows us to deploy 320 Ceph OSD Daemons. Lets assume a 42U rack with 2U nodes,
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leaving an extra 2U for a rack switch.
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.sp
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To reflect our hierarchy of devices, nodes, racks and rows, we would execute
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the following:
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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$ crushtool \-o crushmap \-\-build \-\-num_osds 320 \e
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node straw 4 \e
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rack straw 20 \e
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row straw 2 \e
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root straw 0
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# id weight type name reweight
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\-87 320 root root
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\-85 160 row row0
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\-81 80 rack rack0
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\-1 4 node node0
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0 1 osd.0 1
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1 1 osd.1 1
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2 1 osd.2 1
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3 1 osd.3 1
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\-2 4 node node1
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4 1 osd.4 1
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5 1 osd.5 1
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\&...
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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CRUSH rulesets are created so the generated crushmap can be
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tested. They are the same rulesets as the one created by default when
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creating a new Ceph cluster. They can be further edited with:
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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# decompile
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crushtool \-d crushmap \-o map.txt
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# edit
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emacs map.txt
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# recompile
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crushtool \-c map.txt \-o crushmap
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.SH AVAILABILITY
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.sp
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\fBcrushtool\fP is part of the Ceph distributed storage system. Please
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refer to the Ceph documentation at \fI\%http://ceph.com/docs\fP for more
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information.
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.SH SEE ALSO
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.sp
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\fBceph\fP(8),
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\fBosdmaptool\fP(8),
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.SH AUTHORS
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.sp
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John Wilkins, Sage Weil, Loic Dachary
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.SH COPYRIGHT
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2010-2014, Inktank Storage, Inc. and contributors. Licensed under Creative Commons BY-SA
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