Redis could be safer on 32bit instances

Hello list!

I think we have a problem with Redis running on 32 bit, since if the
configuration is not ok, there is some operational risk due to hard
4GB limit, resulting in out of memory (one thing that without 32bit
instances rarely happens at all, since Linux will often overcommit
instead, causing just slowdowns that are MUCH better than an exit for
out of memory).

Today I was following tweets from Thomas (@tqbf on twitter) that was
having problem with Redis 32 bit instances, to summarize:

* Put too much data inside -> over 4GB limit reached
* OOM
* Halt
* Corrupted AOF
* AOF unfixable on 32 bit machine.

This is not good, there are different solutions, from a default limit
with 32 bit instances to 3GB of max memory, to simple warnings, to
more documentation about how properly configure a 32 bit instance for
data safety.

Also I'm not sure when AOF is unfixable on 32 bit machines, maybe our
check dump utility uses data types that are 32 bit so will overflow or
alike?

Btw I don't want to summarize everything in this message, but it is
just an input in order to start a discussion to get this fixed for
Redis 2.6.

Also I'm happy to announce the 2011 Redis Moka Award winners ->
http://antirez.com/post/redis-moka-awards-2011.html
In general I want to say thank to to the Redis community, especially
to the award winners and to people helping here in this google group,
for the wonderful work done in the course of 2011.

Cheers,
Salvatore



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