Memcached vs Redis - More Different Than You Would Expect

1

memcached

So knowing how the difference between Redis and memcached in-memory usage, lets see what this means. Memcached slabs once assigned never change their size. This means it is possible to poison your memcached cluster and really waste memory. If you load your empty memcached cluster with lots of 1 MB items, then all of the slabs will be allocated to that size. Adding a 80 KB item once this happens will end up with your 80 KB item sitting in a 1 MB chunk wasting the majority of it's memory. Slabs can be reassigned if they are emptied, so your milage may vary depending on your TTL values and how you access items.

#Key-Value Database #Databases #NoSQL Databases 29 social mentions

2

Redis

Remember when I wrote about how Redis was using malloc to assign memory? I lied. While Redis did use malloc at some point, these days Redis actually uses jemalloc. The reason for this is that jemalloc, while having lower peak performance has lower memory fragmentation helping to solve the framented memory issues that Redis experiences.

#Key-Value Database #NoSQL Databases #Databases 185 social mentions