Difference between revisions of "IBM CMOD Cache Filesystems"

As you load data into IBM Content Manager OnDemand, data is placed into the caches for fast access.  The only exception to this rule is if you choose not to load Application Group data to the cache at all, and send them directly to secondary storage - which is generally reserved for situations where documents need to be archived for legal or regulatory reasons, but are rarely, if ever, accessed.

You can reduce the amount of data in the cache filesystems with the [[arsmaint]] command.  You will want to migrate any data with the <code>arsmaint -m </code> command first, then run the <code>arsmaint -c</code> command to delete eligible items from the cache.  You can combine both options in the same command (<code>arsmaint -mc </code>) to perform both tasks.

CMOD Cache expiration is the process by which OnDemand reduces the amount of data inside the caches, in order to make room for new data that is loaded into your Content Manager OnDemand server.  It does this by removing data that has already been migrated to secondary storage or is eligible for expiration, starting with the oldest documents first, until the filesystems are approximately 80% full by default.  As mentioned above, on large IBM CMOD servers that have multiple terabytes of cache, adjusting the minimum and maximum parameters makes optimal use of your expensive cache filesystems.  You can visit the [[arsmaint]] page to find out more about how you can clear data from the IBM CMOD cache filesystem.

Storage is expensive and finite.  In order to make the most out of the storage space you have in your IBM CMOD Cache filesystems, you should try to store more of the data that users are actually accessing, for the period of time that they’re interested in them.  You can optimize the cache contents so that you’re using precisely enough disk to perform the required retrievals and to have enough space to load new data.  An optimized cache contains only the data people are accessing.  Unfortunately, there's no built-in tool for performing the Content Manager OnDemand Cache.

If your IBM CMOD Cache Filesystems are large (over 1 terbyte) then the default setting for the <code>arsmaint -c </code> will leave 20% - 200 gigabytes of empty cache.  If you have multiple 1TB cache filesytems, and you only load 20GB per day, you could have a huge amount of wasted space in your caches.  You can adjust this number with the <code>-m </code> and <code>-n </code> options for [[arsmaint]] to set new maximum and minimum caches sizes during cache expiration.

The other ways to tune the cache filesystems are to analyse the patterns of retrievals of Application Group data, and change the cache retention to match actual end user usage, and to use data from your load and retrieval patterns to determine your optimal cache size.  If you need help optimizing your cache filesystem, visit [https://CMOD.cloud/ibm-cmod-cache-optimization CMOD Cloud’s Cache Optimization page].

NO!  The cache is only to be managed withthe [[arsmaint]] utility to reduce the amount of data stored in your cache filesystems, and make space for new documents in the cache.

Content Manager OnDemand automatically balances the amount of data in caches by placing new CMOD object files in the cache with the most free space, measured in blocks of free space in the filesystem.  If you have a large number of cache filesystems with dramatically different utilization, see this article on [https://CMOD.cloud/cache-consolidation Cache Consiolidation].