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?
Thanks, pwr
I guess the caches can be different always their values be upper the required for a correct performance in all the machines.
Regards, Moses
2013/2/21 Patrick Raspante patrickraspante@gmail.com
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?
Thanks, pwr
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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.
On 02/21/2013 08:27 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 is a tool which you can use to monitor the caches:
https://github.com/richm/scripts/wiki/dbmon.sh https://github.com/richm/scripts/blob/master/dbmon.sh
Thanks, pwr
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I was mostly curious if the difference in cache configurations has any negative effect on the integrity of the replication agreement between the directory instances.
To illustrate, say one directory instance is managing several root suffixes and has increased cache settings. The other instance has default settings. The default instance is perfectly capable of operating on the replicated data-set and/or doesn't have the performance requirements of the other instance.
Thanks, Patrick
On Thu, Feb 21, 2013 at 12:39 PM, Rich Megginson rmeggins@redhat.comwrote:
On 02/21/2013 08:27 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 is a tool which you can use to monitor the caches:
https://github.com/richm/scripts/wiki/dbmon.sh https://github.com/richm/scripts/blob/master/dbmon.sh
Thanks, pwr
-- 389 users mailing list389-users@lists.fedoraproject.orghttps://admin.fedoraproject.org/mailman/listinfo/389-users
On 2/21/2013 11:11 AM, Patrick Raspante wrote:
I was mostly curious if the difference in cache configurations has any negative effect on the integrity of the replication agreement between the directory instances.
To illustrate, say one directory instance is managing several root suffixes and has increased cache settings. The other instance has default settings. The default instance is perfectly capable of operating on the replicated data-set and/or doesn't have the performance requirements of the other instance.
No, totally unrelated.
It would be wise to be careful that your replicas can keep up with the changes propagated to them over the long term (otherwise a long queue of changes waiting to be re-played on the replica can build up). You'd be more interested in I/O performance for that though, and this would only be a concern in a very large, very high traffic deployment and in that case you'd have many other things to worry about besides cache size...
On 02/21/2013 11:11 AM, Patrick Raspante wrote:
I was mostly curious if the difference in cache configurations has any negative effect on the integrity of the replication agreement between the directory instances.
To illustrate, say one directory instance is managing several root suffixes and has increased cache settings. The other instance has default settings. The default instance is perfectly capable of operating on the replicated data-set and/or doesn't have the performance requirements of the other instance.
It depends where your requests are going. If all of your servers have an equal request load, then it makes sense to have the same cache settings on all of your servers.
But I strongly encourage you to use the tool below to monitor your usage. Depending on your platform, how much RAM you have, how many entries you have, etc. you may need to decrease your cache settings to save RAM, or increase to cache more entries. To emphasize what David Boreham said, if you can easily cache everything in RAM, in db cache and entry/dn caches, then that will give you the very best performance. Otherwise, better to let the OS file system cache work for you.
Thanks, Patrick
On Thu, Feb 21, 2013 at 12:39 PM, Rich Megginson <rmeggins@redhat.com mailto:rmeggins@redhat.com> wrote:
On 02/21/2013 08:27 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 is a tool which you can use to monitor the caches: https://github.com/richm/scripts/wiki/dbmon.sh https://github.com/richm/scripts/blob/master/dbmon.shThanks, pwr -- 389 users mailing list 389-users@lists.fedoraproject.org <mailto:389-users@lists.fedoraproject.org> https://admin.fedoraproject.org/mailman/listinfo/389-users
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