This issue has to be looked from a micro and macro level. On the microlevel
the "best" way is workload specific. On the macro level this mostly boils
down to data and memory size.
Companions are going to churn cache, this is unavoidable. Imho solid state
makes the micro optimization meanless in th
On Thu, Dec 6, 2012 at 7:36 PM, aaron morton wrote:
> So for memory mapped files, compaction can do a madvise SEQUENTIAL instead
> of current DONTNEED flag after detecting appropriate OS versions. Will this
> help?
>
>
> AFAIK Compaction does use memory mapped file access.
The history :
https://
> So for memory mapped files, compaction can do a madvise SEQUENTIAL instead of
> current DONTNEED flag after detecting appropriate OS versions. Will this help?
AFAIK Compaction does use memory mapped file access.
Cheers
-
Aaron Morton
Freelance Cassandra Developer
New Zealand
Thanks Aaron,
I found the implementation in CLibrary.trySkipCache() method which uses
fadvise DONTNEED flag after going through
https://issues.apache.org/jira/browse/CASSANDRA-1470
I also came across the link mentioned in JIRA
http://blog.mikemccandless.com/2010/06/lucene-and-fadvisemadvise.html?
Background http://en.wikipedia.org/wiki/Memory-mapped_file
> Is it going to load only relevant pages per SSTable on read or is it going to
> load an entire SSTable on first access?
It will load what is requested, and maybe some additional data taking into
account the amount of memory available f
Thanks Aaron,
I am not quite clear on how MMap loads SSTables other than the fact that it
kicks in only during a first-time access
Is it going to load only relevant pages per SSTable on read or is it going
to load an entire SSTable on first access?
Say suppose compaction kicks in. Will it then e
> Will MMapping data files be detrimental for reads, in this case?
No.
> In general, when should we opt for MMap data files and what are the factors
> that need special attention when enabling the same?
mmapping is the default, so I would say use it until you have a reason not to.
mmapping wil
