I’d advise keeping read ahead low… or turning it off on SSD. Also, noop IO
scheduler might help you on that disk..
IF Cassandra DOES perform a contiguous read, read ahead won’t be helpful.
It’s essentially obsolete now on SSDs.
On Wed, Sep 24, 2014 at 1:20 PM, Daniel Chia wrote:
> Cassandra o
Cassandra only reads a small part of each SSTable during normal operation
(not compaction), in fact Datastax recommends lowering readahead -
http://www.datastax.com/documentation/cassandra/2.1/cassandra/install/installRecommendSettings.html
There are also blogposts where people have improved their
"does it typically have to read in the entire SStable into memory (assuming
the bloom filter said yes)?" --> No, it would be perf killer.
On the read path, after Bloom filter, Cassandra is using the "Partition
Key Cache" to see if the partition it is looking for is present there.
If yes, it get
We're using cassandra as a key-value store; our values are small. So we're
thinking we don't need much disk readahead (e.g., "blockdev -getra /dev/sda").
We're using SSDs.
When cassandra does disk seeks to satisfy read requests does it typically have
to read in the entire SStable into memory
