incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Sameer Farooqui <sam...@blueplastic.com>
Subject Re: Question about SizeTieredCompactionStrategy in C* 2.0: not all SSTables are being compacted
Date Tue, 08 Oct 2013 19:46:52 GMT
Hmm, good point. I'll test this out again and see the compaction behavior
is as expected given the relative sizes of the SSTables.




On Tue, Oct 8, 2013 at 3:06 PM, Tyler Hobbs <tyler@datastax.com> wrote:

> Well, 6 was created by the other sstables being compacted, correct?  If
> so, they were probably quite a bit smaller (~25% of the size).  Once you
> have two more sstables of roughly that size, they should be compacted
> automatically.
>
>
> On Tue, Oct 8, 2013 at 2:01 PM, Sameer Farooqui <sameer@blueplastic.com>wrote:
>
>> Thanks for the reply, Tyler. I thought that too.. that maybe the SSTables
>> are mismatched in size... but upon closer inspection, that doesn't appear
>> to be the case:
>>
>> -rw-r--r-- 1 cassandra cassandra  227 Oct  7 23:26
>> demodb-users-jb-1-Data.db
>> -rw-r--r-- 1 cassandra cassandra  242 Oct  8 00:38
>> demodb-users-jb-6-Data.db
>>
>>
>> The two files look to be nearly the same size. There just appears to be
>> something special about that first SSTable and it not getting compacted.
>>
>>
>> On Tue, Oct 8, 2013 at 2:49 PM, Tyler Hobbs <tyler@datastax.com> wrote:
>>
>>> SizeTieredCompactionStrategy only compacts sstables that are a similar
>>> size (by default, they basically need to be within 50% of each other).
>>> Perhaps your first SSTable was very large or small compared to the others?
>>>
>>>
>>> On Mon, Oct 7, 2013 at 8:06 PM, Sameer Farooqui <sameer@blueplastic.com>wrote:
>>>
>>>> Hi,
>>>>
>>>> I have a fresh 1-node C* 2.0 install with a demo keyspace created with
>>>> the SizeTiered compaction strategy.
>>>>
>>>> I've noticed that in the beginning this keyspace has just one SSTable:
>>>> demodb-users-jb-1-Data.db
>>>>
>>>> But as I add more data to the table and do some flushes, the # of
>>>> SSTables builds up. After I have a handful of SSTables, I trigger a flush
>>>> using 'nodetool flush demodb users', but then not ALL of the SSTables get
>>>> compacted.
>>>>
>>>> I've noticed that the 1st SSTable remains the same and doesn't
>>>> disappear after the compaction, but the latter SSTables do get compacted
>>>> into one new Data file.
>>>>
>>>> Is there a reason why the first SSTable is special and it is not
>>>> disappearing after compaction?
>>>>
>>>> Also, I think I noticed that if I wait a few days and run another
>>>> compaction, then that 1st SSTable does not compacted (and it disappears).
>>>>
>>>> Can someone help explain why the 1st SSTable behaves this way?
>>>>
>>>
>>>
>>>
>>> --
>>> Tyler Hobbs
>>> DataStax <http://datastax.com/>
>>>
>>
>>
>
>
> --
> Tyler Hobbs
> DataStax <http://datastax.com/>
>

Mime
View raw message