On 7/12/2011 10:19 AM, Peter Schuller wrote:
Do any Cass developers have any thoughts on this and whether or not it would
be helpful considering Cass' architecture and operation?
A well-functioning L2 cache should definitely be very useful with
Cassandra for read-intensive workloads where the request distribution
is such that additional caching will be beneficial. However, it will
depend in any particular case on how the L2 cache works, and what your
request distribution is like.
I have been wanting to try flashcache but haven't yet, so I cannot speak to it.
In particular though, keep in mind that if you've got say 1 tb of data
and your memory is enough to keep the hot set, and you're disk I/O is
coming form the long tail, increasing the amount of cache to 200 gig
may not necessarily give you a huge improvement in terms of
percentages.
Thanks Peter, but... hmmm, are you saying that even after a cache miss
which results in a disk read and blocks being moved to the ssd, that by
the next cache miss for the same data and subsequent same file blocks,
that the ssd is unlikely to have those same blocks present anymore?
