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diff --git a/src/ceph/doc/dev/erasure-coded-pool.rst b/src/ceph/doc/dev/erasure-coded-pool.rst deleted file mode 100644 index 4694a7a..0000000 --- a/src/ceph/doc/dev/erasure-coded-pool.rst +++ /dev/null @@ -1,137 +0,0 @@ -Erasure Coded pool -================== - -Purpose -------- - -Erasure-coded pools require less storage space compared to replicated -pools. The erasure-coding support has higher computational requirements and -only supports a subset of the operations allowed on an object (for instance, -partial write is not supported). - -Use cases ---------- - -Cold storage -~~~~~~~~~~~~ - -An erasure-coded pool is created to store a large number of 1GB -objects (imaging, genomics, etc.) and 10% of them are read per -month. New objects are added every day and the objects are not -modified after being written. On average there is one write for 10,000 -reads. - -A replicated pool is created and set as a cache tier for the -erasure coded pool. An agent demotes objects (i.e. moves them from the -replicated pool to the erasure-coded pool) if they have not been -accessed in a week. - -The erasure-coded pool crush ruleset targets hardware designed for -cold storage with high latency and slow access time. The replicated -pool crush ruleset targets faster hardware to provide better response -times. - -Cheap multidatacenter storage -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Ten datacenters are connected with dedicated network links. Each -datacenter contains the same amount of storage with no power-supply -backup and no air-cooling system. - -An erasure-coded pool is created with a crush map ruleset that will -ensure no data loss if at most three datacenters fail -simultaneously. The overhead is 50% with erasure code configured to -split data in six (k=6) and create three coding chunks (m=3). With -replication the overhead would be 400% (four replicas). - -Interface ---------- - -Set up an erasure-coded pool:: - - $ ceph osd pool create ecpool 12 12 erasure - -Set up an erasure-coded pool and the associated crush ruleset:: - - $ ceph osd crush rule create-erasure ecruleset - $ ceph osd pool create ecpool 12 12 erasure \ - default ecruleset - -Set the ruleset failure domain to osd (instead of the host which is the default):: - - $ ceph osd erasure-code-profile set myprofile \ - crush-failure-domain=osd - $ ceph osd erasure-code-profile get myprofile - k=2 - m=1 - plugin=jerasure - technique=reed_sol_van - crush-failure-domain=osd - $ ceph osd pool create ecpool 12 12 erasure myprofile - -Control the parameters of the erasure code plugin:: - - $ ceph osd erasure-code-profile set myprofile \ - k=3 m=1 - $ ceph osd erasure-code-profile get myprofile - k=3 - m=1 - plugin=jerasure - technique=reed_sol_van - $ ceph osd pool create ecpool 12 12 erasure \ - myprofile - -Choose an alternate erasure code plugin:: - - $ ceph osd erasure-code-profile set myprofile \ - plugin=example technique=xor - $ ceph osd erasure-code-profile get myprofile - k=2 - m=1 - plugin=example - technique=xor - $ ceph osd pool create ecpool 12 12 erasure \ - myprofile - -Display the default erasure code profile:: - - $ ceph osd erasure-code-profile ls - default - $ ceph osd erasure-code-profile get default - k=2 - m=1 - plugin=jerasure - technique=reed_sol_van - -Create a profile to set the data to be distributed on six OSDs (k+m=6) and sustain the loss of three OSDs (m=3) without losing data:: - - $ ceph osd erasure-code-profile set myprofile k=3 m=3 - $ ceph osd erasure-code-profile get myprofile - k=3 - m=3 - plugin=jerasure - technique=reed_sol_van - $ ceph osd erasure-code-profile ls - default - myprofile - -Remove a profile that is no longer in use (otherwise it will fail with EBUSY):: - - $ ceph osd erasure-code-profile ls - default - myprofile - $ ceph osd erasure-code-profile rm myprofile - $ ceph osd erasure-code-profile ls - default - -Set the ruleset to take ssd (instead of default):: - - $ ceph osd erasure-code-profile set myprofile \ - crush-root=ssd - $ ceph osd erasure-code-profile get myprofile - k=2 - m=1 - plugin=jerasure - technique=reed_sol_van - crush-root=ssd - |