Re: mysql

On Apr 4, 2005 7:11 PM, David <thump_at_cosmiccooler.org> wrote:
> What are the largest pros and cons involved in discussing mysql versus
> Oracle?

MySQL doesn't have the recoverability features of Oracle, you lose a disk and you've lost everything since the last backup. WikiPedia recently lost 2 days of updates when they lost a 'disk' (actually a RAID arrary presented as a virtualdisk) with their MySQL data on, it took them a day and a half to get up and running again. LiveJournal, in January, didn't lose any data when their CoLo company lost power but did take 3 days to get a working system back. They didn't lose data because their middleware had features to make up for the lack in MySQL. Still, a 3 day outage for a power loss of less than 1 hour is really not good.

MySQL scaling is a joke. High volume sites (such as WikiPedia and LiveJournal) scale by running many servers in paralell then implementing bespoke replication and multiple master-slave (typically reads go to the slaves and writes to the masters, periodically the slaves pull updates from the Masters) clusters. This works well where reads massively out number writes but quickly gets bottlenecked on writes (as can be seen when trying to post a journal entry on LiveJournal at peak times, it presents as a server busy error).

MySQL was originally developed by a supermarket (as I recall) for use in daily reporting, essentially a datamart. The day's transactions would be loaded in and summaries generated then the reports would be run. If the database got fried then they still had the original files so could rebuild it easily. All releases have carried that original assumption forward. Not very suitable for OLTP use.

Stephen

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