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I like the idea of Redis but it has the obvious limitation that it can only be used when the data you're working with will absolutely never grow bigger than ava
by papaf 17y ago
I like the idea of Redis but it has the obvious limitation that it can only be used when the data you're working with will absolutely never grow bigger than available memory. This not only reduces the problems it can be used on but makes the Twitter example given on the Redis website very unrealistic.
- antirez 17y agoHello papaf. If you try to do the math of the number of messages you can hold using four 64 GB Linux boxes you'll find that it's a perfectly viable (and very scalable) solution to use Redis in a number of real-world scenarios. Note that with this setup you don't need N additional memcached servers, so all the $ can be spent in RAM for the DBs. Im my personal experience with high traffic web services what I discovered is that anyway when the on-disk dataset starts to get bigger than the available RAM performances are horrible anyway. Also note that when there is a lot of data to Index, the right thing to do can be the following: take all the metadata on Redis, for fast access. Take the "bulk" data on MySQL, just an incremental ID + Blob field. Perform queries against both. It is absolutely possible to add some kind of aging algorithm to swap not recently used keys on disk to Redis in order to allow for bigger than RAM datasets, but most people dealing with high traffic sites told me "don't do it, it's useless because we have access patterns that are more or less evenly distributed among the key space".
- simonw 17y agoJust out of interest, do you know what the largest Redis instance in production is? It would be fascinating to hear a case study about a real-life 16GB+ store.
- antirez 17y agoI don't know if they ever continued to use it in production, but there was a guy experimenting with a number of 128 GB Redis servers :) This guy found most of the bugs with huge datasets, and thanks to his work Redis 1.01 was tested in extreme conditions.
- mahmud 17y agoantirez, Keep up the good work. Some of us know what we're doing and we're using Redis as a cheap reliable message queue :-) grazie per tutto!
- antirez 17y agograzie a te ;)
- leej 17y agoDo you think there will be considerable performance difference when using Redis instead of a two column MySQL table for this purpose? What is the utility of using Redis there?