RepoMirrors/ceph
1
0
Fork 0
mirror of https://github.com/ceph/ceph synced 2025-01-20 01:51:34 +00:00
Code Issues Packages Projects Releases Wiki Activity

doc/rados: erasure-code-lrc corrections

Browse Source 
doc/rados: erasure-code-lrc corrections

- Clarified / corrected jerasure recovery characterization cf. https://library.eecs.utk.edu/storage/125phpw0xFqAut-cs-07-603.pdf
- Capitalization
- Word choice:  OSDs are discrete / cardinal, so "fewer" instead of  "less"
- Reworked a few phrases to be less stilted

Signed-off-by: Anthony D'Atri <anthony.datri@gmail.com>
This commit is contained in:
Anthony D'Atri 2020-09-28 23:42:10 -07:00 committed by GitHub
parent 5865352387
commit e7afd9017d
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 9 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
doc/rados/operations/erasure-code-lrc.rst
View File

@ -4,12 +4,12 @@ Locally repairable erasure code plugin
With the *jerasure* plugin, when an erasure coded object is stored on
multiple OSDs, recovering from the loss of one OSD requires reading
from all the others. For instance if *jerasure* is configured with
*k=8* and *m=4*, losing one OSD requires reading from the eight
others to repair.
from *k* others. For instance if *jerasure* is configured with
*k=8* and *m=4*, recovering from the loss of one OSD requires reading
from eight others.
The *lrc* erasure code plugin creates local parity chunks to be able
to recover using less OSDs. For instance if *lrc* is configured with
The *lrc* erasure code plugin creates local parity chunks to enable
recovery using fewer surviving OSDs. For instance if *lrc* is configured with
*k=8*, *m=4* and *l=4*, it will create an additional parity chunk for
every four OSDs. When a single OSD is lost, it can be recovered with
only four OSDs instead of eight.
@ -34,7 +34,7 @@ observed.::
Reduce recovery bandwidth between racks
---------------------------------------
In Firefly the reduced bandwidth will only be observed if the primary
In Firefly the bandwidth reduction will only be observed if the primary
OSD is in the same rack as the lost chunk.::
$ ceph osd erasure-code-profile set LRCprofile \
@ -106,7 +106,7 @@ Where:
``crush-locality={bucket-type}``
:Description: The type of the crush bucket in which each set of chunks
:Description: The type of the CRUSH bucket in which each set of chunks
defined by **l** will be stored. For instance, if it is
set to **rack**, each group of **l** chunks will be
placed in a different rack. It is used to create a
@ -158,8 +158,8 @@ Low level plugin configuration
==============================
The sum of **k** and **m** must be a multiple of the **l** parameter.
The low level configuration parameters do not impose such a
restriction and it may be more convenient to use it for specific
The low level configuration parameters however do not enforce this
restriction and it may be advantageous to use them for specific
purposes. It is for instance possible to define two groups, one with 4
chunks and another with 3 chunks. It is also possible to recursively
define locality sets, for instance datacenters and racks into