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Add Write-behind (write-back) section

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Donne Martin 2017-03-01 20:38:17 -08:00
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README.md
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@ -1347,3 +1347,21 @@ Write-through is a slow overall operation due to the write operation, but subseq
* When a new node is created due to failure or scaling, the new node will not cache entries until the entry is updated in the database. Cache-aside in conjunction with write through can mitigate this issue. * When a new node is created due to failure or scaling, the new node will not cache entries until the entry is updated in the database. Cache-aside in conjunction with write through can mitigate this issue.
* Most data written might never read, which can be minimized with a TTL. * Most data written might never read, which can be minimized with a TTL.
#### Write-behind (write-back)
<p align="center">
<img src="http://i.imgur.com/rgSrvjG.png">
<br/>
<i><a href=http://www.slideshare.net/jboner/scalability-availability-stability-patterns/>Source: Scalability, availability, stability, patterns</a></i>
</p>
In write-behind, tha application does the following:
* Add/update entry in cache
* Asynchronously write entry to the data store, improving write performance
##### Disadvantage(s): write-behind
* There could be data loss if the cache goes down prior to its contents hitting the data store.
* It is more complex to implement write-behind than it is to implement cache-aside or write-through.