cloud init: use expected disk number in example

[pve-docs.git] / pveceph.adoc

diff --git a/pveceph.adoc b/pveceph.adoc
index 870ca6c5da5b863d6605c049860babfe95386c56..fdd4cf679ee64f89156ae9196a94e78af838c4aa 100644 (file)
--- a/pveceph.adoc
+++ b/pveceph.adoc
@@ -499,7 +499,7 @@ make better decisions.
 .Example for creating a pool over the CLI
 [source,bash]
 ----
 .Example for creating a pool over the CLI
 [source,bash]
 ----

-pveceph pool create <name> --add_storages
+pveceph pool create <pool-name> --add_storages

 ----
 
 TIP: If you would also like to automatically define a storage for your
 ----
 
 TIP: If you would also like to automatically define a storage for your


@@ -548,16 +548,28 @@ manual.
 
 
 [[pve_ceph_ec_pools]]
 
 
 [[pve_ceph_ec_pools]]

-Erasure Coded (EC) Pools
-~~~~~~~~~~~~~~~~~~~~~~~~
+Erasure Coded Pools
+~~~~~~~~~~~~~~~~~~~

 
 

-Erasure coded (EC) pools can offer more usable space for the price of
-performance. In replicated pools, multiple replicas of the data are stored
-(`size`). In erasure coded pool, data is split into `k` data chunks with
-additional `m` coding chunks.  The coding chunks can be used to recreate data
-should data chunks be missing.  The number of coding chunks, `m`, defines how
-many OSDs can be lost without losing any data.  The total amount of objects
-stored is `k + m`.
+Erasure coding (EC) is a form of `forward error correction' codes that allows
+to recover from a certain amount of data loss. Erasure coded pools can offer
+more usable space compared to replicated pools, but they do that for the price
+of performance.
+
+For comparison: in classic, replicated pools, multiple replicas of the data
+are stored (`size`) while in erasure coded pool, data is split into `k` data
+chunks with additional `m` coding (checking) chunks. Those coding chunks can be
+used to recreate data should data chunks be missing.
+
+The number of coding chunks, `m`, defines how many OSDs can be lost without
+losing any data. The total amount of objects stored is `k + m`.
+
+Creating EC Pools
+^^^^^^^^^^^^^^^^^
+
+Erasure coded (EC) pools can be created with the `pveceph` CLI tooling.
+Planning an EC pool needs to account for the fact, that they work differently
+than replicated pools.

 
 The default `min_size` of an EC pool depends on the `m` parameter. If `m = 1`,
 the `min_size` of the EC pool will be `k`. The `min_size` will be `k + 1` if
 
 The default `min_size` of an EC pool depends on the `m` parameter. If `m = 1`,
 the `min_size` of the EC pool will be `k`. The `min_size` will be `k + 1` if


@@ -580,7 +592,7 @@ To create a new EC pool, run the following command:
 
 [source,bash]
 ----
 
 [source,bash]
 ----

-pceveph pool create <pool name> --erasure-coding k=2,m=1
+pveceph pool create <pool-name> --erasure-coding k=2,m=1

 ----
 
 Optional parameters are `failure-domain` and `device-class`. If you
 ----
 
 Optional parameters are `failure-domain` and `device-class`. If you


@@ -601,11 +613,6 @@ If you need to change the `min_size` on the data pool, you can do it later.
 The `size` and `crush_rule` parameters cannot be changed on erasure coded
 pools.
 
 The `size` and `crush_rule` parameters cannot be changed on erasure coded
 pools.
 

-[source,bash]
-----
-pvesm add rbd <storage name> --pool <replicated pool> --data-pool <ec pool>
-----
-

 If there is a need to further customize the EC profile, you can do so by
 creating it with the Ceph tools directly footnote:[Ceph Erasure Code Profile
 {cephdocs-url}/rados/operations/erasure-code/#erasure-code-profiles], and
 If there is a need to further customize the EC profile, you can do so by
 creating it with the Ceph tools directly footnote:[Ceph Erasure Code Profile
 {cephdocs-url}/rados/operations/erasure-code/#erasure-code-profiles], and


@@ -614,9 +621,22 @@ specify the profile to use with the `profile` parameter.
 For example:
 [source,bash]
 ----
 For example:
 [source,bash]
 ----

-pceveph pool create <pool name> --erasure-coding profile=<profile name>
+pveceph pool create <pool-name> --erasure-coding profile=<profile-name>
+----
+
+Adding EC Pools as Storage
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+You can add an already existing EC pool as storage to {pve}. It works the same
+way as adding an `RBD` pool but requires the extra `data-pool` option.
+
+[source,bash]
+----
+pvesm add rbd <storage-name> --pool <replicated-pool> --data-pool <ec-pool>

 ----
 
 ----
 

+TIP: Do not forget to add the `keyring` and `monhost` option for any external
+Ceph clusters, not managed by the local {pve} cluster.

 
 Destroy Pools
 ~~~~~~~~~~~~~
 
 Destroy Pools
 ~~~~~~~~~~~~~


@@ -741,7 +761,7 @@ ceph osd crush rule create-replicated <rule-name> <root> <failure-domain> <class
 [frame="none",grid="none", align="left", cols="30%,70%"]
 |===
 |<rule-name>|name of the rule, to connect with a pool (seen in GUI & CLI)
 [frame="none",grid="none", align="left", cols="30%,70%"]
 |===
 |<rule-name>|name of the rule, to connect with a pool (seen in GUI & CLI)

-|<root>|which crush root it should belong to (default ceph root "default")
+|<root>|which crush root it should belong to (default Ceph root "default")

 |<failure-domain>|at which failure-domain the objects should be distributed (usually host)
 |<class>|what type of OSD backing store to use (e.g., nvme, ssd, hdd)
 |===
 |<failure-domain>|at which failure-domain the objects should be distributed (usually host)
 |<class>|what type of OSD backing store to use (e.g., nvme, ssd, hdd)
 |===


@@ -923,7 +943,7 @@ servers.
 pveceph fs destroy NAME --remove-storages --remove-pools
 ----
 +
 pveceph fs destroy NAME --remove-storages --remove-pools
 ----
 +

-This will automatically destroy the underlying ceph pools as well as remove
+This will automatically destroy the underlying Ceph pools as well as remove

 the storages from pve config.
 
 After these steps, the CephFS should be completely removed and if you have
 the storages from pve config.
 
 After these steps, the CephFS should be completely removed and if you have