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From Tore Halset <hal...@pvv.ntnu.no>
Subject Re: Indexed Disk Cache safe copying of files
Date Wed, 17 Jun 2009 20:35:11 GMT
Hello.

I do this in my jcs cache. The items in the cache is 0-30MB each. The  
total volume is ~20GB. Instead of the standard indexed disc cache, I  
use a file based cache. The key is converted to a filename and each  
item is stored as a separate file. Several jvms can share the same  
cache and the cache can be rsynced between nodes while running the  
application.

This setup might be slow for caches with lots of small objects, but it  
works very well with my setup.

The source code is attached to this issue:
https://issues.apache.org/jira/browse/JCS-58

To be able to hold as many objects as possible in ram without getting  
OutOfMemoryException, I use this cache with a soft reference cache.
https://issues.apache.org/jira/browse/JCS-54

Regards,
  - Tore.

On Jun 17, 2009, at 10:23, Silvano wrote:

> Since we have a large cache that needs significant time to be  
> populated, we need to be able to copy the files of the regions  
> configured as Indexed Disk Cache between different installations.
> We believe this can be done safely if we turn off the jvm, but we  
> would need to copy safely the files while the jvm is running.  
> However it seems that the key files are written only when you turn  
> off the jvm (at least the size changes when we turn off the jvm, so  
> we suspect that they are not synchronized to disk in normal  
> operations).
>
> We can make sure at application level that nobody writes in the  
> cache during the file copy process, but is this sufficient?
>
> Can anybody recommend a solution to this issue?
>
> Best regards,
>   Silvano.
>
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