ZODB Read and Writes
There is a difference between ZODB read and write performance. ZODB is generally considered best for applicaiotns that have more reads than writes. Web applicatins are usually like that. Banking applications or airline reservations systems should use a different technology.
So how do reads work? ZODB runs off of a single file. Reads can be all over the file, writes are only at the end of the file. Since a single file can be distributed across multiple hard drive spindles, in principal read parallelism is possible, but in practice the read spead is limited by the speed of the ZEO server process. Writes are different. ZODB only writes to the end of a file. Writes may run into conflicts, and require retries. So that limits the write performance of the ZODB.
And of course the server caches data from the disk, and that also has a big impact on performance.
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