On 2/21/2013 8:27 AM, Patrick Raspante wrote:
Is it required (or at least suggested) that multi-mastered directory server instances have the equal values for dbcache and entry cache settings? If so, what adverse effects result from not configuring the caches similarly?
There's no relationship like the one you're suggesting. You can configure any size for each kind of cache.
These days, (now that computers are so much bigger and faster than when the DS was originally designed), unless you're looking for the last fraction of performance from your deployment, I'd suggest leaving the cache sizes at the default. This will push most of the caching down into the filesystem, which will do a reasonably good job with the big benefit that you won't need to spend time worrying about and futzing with the cache sizing.
Remember that the entry cache holds entry content (not index data), in memory, in the "decoded state". So if you're looking to serve 10's of thousands of entries per second from a server, it helps to have them in the entry cache because you're saving the cost to read the entry data from the filesystem cache and decode it from ascii ldif to the avl tree memory format. This might amount to 1us or more per entry, for every entry touched that is not found in the entry cache.
The DB cache by contrast holds pages of database content (entries + any referenced index data) in memory. So it saves (only) the cost to copy the page from the filesystem cache - the payload data is just a copy of the on-disk data.
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