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Posted to user@cassandra.apache.org by Mubarak Seyed <mu...@gmail.com> on 2010/09/07 08:33:19 UTC
Flush and compaction happens frequently
I have a 8 nodes cluster, MemtableThreshold is 2 GB/CF, MemtableObjectsCount
is 1.2, heap (min/max) is 30 GB and only 4 ColumnFamilies
It appears from system.log that flush happens for every < 50 operations
(read or write) and compaction is happening very frequently and i could see
lots of sstable is getting created (with smaller size). For a just 1000
inserts, i could see around 20 sstables.
When i change the MemtableThreshold to 1 GB/CF, everything works as desired.
Any idea, what could be the problem when i specify MemtableThreshold to 2
GB/CF even though i specified the large heap?
--
Thanks,
Mubarak Seyed.
Re: Flush and compaction happens frequently
Posted by aaron morton <aa...@thelastpickle.com>.
That sounds a little odd, may help if you post the yaml settings, the
tpstats and the log lines that look something like this...
INFO [ROW-MUTATION-STAGE:5] 2010-09-04 15:43:49,402
ColumnFamilyStore.java (line 790) Enqueuing flush of
Memtable-Super1@1754565178(80208 bytes, 2304 operations)
Also wondering why you chose such high memtable thresholds and how
that's working. Do you expect to trigger the operation count or the
throughput count in normal processing? Have you seen the additional
guidance on mem table tuning here
http://wiki.apache.org/cassandra/MemtableThresholds
Aaron
On 7 Sep 2010, at 18:33, Mubarak Seyed wrote:
> I have a 8 nodes cluster, MemtableThreshold is 2 GB/CF, MemtableObjectsCount is 1.2, heap (min/max) is 30 GB and only 4 ColumnFamilies
>
> It appears from system.log that flush happens for every < 50 operations (read or write) and compaction is happening very frequently and i could see lots of sstable is getting created (with smaller size). For a just 1000 inserts, i could see around 20 sstables.
>
> When i change the MemtableThreshold to 1 GB/CF, everything works as desired.
>
> Any idea, what could be the problem when i specify MemtableThreshold to 2 GB/CF even though i specified the large heap?
>
> --
> Thanks,
> Mubarak Seyed.