Using Summary indexing I found a large benefit in terms of performances (also ten times quicker!), for example with BlueCoat logs that have billions of events every day!
Problems are that it's impossible to delete a part of summarized logs, but only the full tsixd file (I asked to Splunk to take in consideration the opportunity to insert the delete functionality), this means that you cannot do errors in summarizing, because you cannot delete them.
In addition using Summary indexing there is a delay in data access because logs are indexed two times and you have to wait that logs are indexed before to summarize them.
In my case I have a larger delay because I have to be sure that logs are really all arrived before summarizing.
There aren't many checks on the summary indexing operation, so there is the risk to index twice a log or lost it.
At the end there is a greater disk space occupation, but in my case is less of the problem.
In conclusion: use it because is really useful but attention!
Bye.
Giuseppe
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