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From "Thomas Mueller (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-926) Global data store for binaries
Date Thu, 30 Aug 2007 14:06:30 GMT

    [ https://issues.apache.org/jira/browse/JCR-926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12523853
] 

Thomas Mueller commented on JCR-926:
------------------------------------

As far as I understand, one (important) use case is to use one workspace for 'authoring' and
another for 'production'. The workspaces contain mostly the same data (maybe 90% is the same).
Having a data store for each workspace would mean having to copy all large files. Having one
data store saves you 50% of the space (for large objects). Also you can move data from one
workspace to the other very quickly (because the files don't have to be copied, only the identifiers).
Also cloning of a workspace is very fast for the same reasons.

> i think to use different workspaces is for us the better way .. 
Do you know about blob store? If not you should try it out, because it sounds like this would
be exactly what you need. The blob store already available.


> Global data store for binaries
> ------------------------------
>
>                 Key: JCR-926
>                 URL: https://issues.apache.org/jira/browse/JCR-926
>             Project: Jackrabbit
>          Issue Type: New Feature
>          Components: core
>            Reporter: Jukka Zitting
>         Attachments: dataStore.patch, DataStore.patch, DataStore2.patch, dataStore3.patch,
dataStore4.zip, dataStore5-garbageCollector.patch, internalValue.patch, ReadWhileSaveTest.patch
>
>
> There are three main problems with the way Jackrabbit currently handles large binary
values:
> 1) Persisting a large binary value blocks access to the persistence layer for extended
amounts of time (see JCR-314)
> 2) At least two copies of binary streams are made when saving them through the JCR API:
one in the transient space, and one when persisting the value
> 3) Versioining and copy operations on nodes or subtrees that contain large binary values
can quickly end up consuming excessive amounts of storage space.
> To solve these issues (and to get other nice benefits), I propose that we implement a
global "data store" concept in the repository. A data store is an append-only set of binary
values that uses short identifiers to identify and access the stored binary values. The data
store would trivially fit the requirements of transient space and transaction handling due
to the append-only nature. An explicit mark-and-sweep garbage collection process could be
added to avoid concerns about storing garbage values.
> See the recent NGP value record discussion, especially [1], for more background on this
idea.
> [1] http://mail-archives.apache.org/mod_mbox/jackrabbit-dev/200705.mbox/%3c510143ac0705120919k37d48dc1jc7474b23c9f02cbd@mail.gmail.com%3e

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