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From AJ>
Subject Re: Anyone using Facebook's flashcache?
Date Tue, 12 Jul 2011 17:30:24 GMT
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?

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