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From Wei Zhu <wz1...@yahoo.com>
Subject Re: Estimating write throughput with LeveledCompactionStrategy
Date Wed, 06 Feb 2013 18:02:41 GMT
I have been struggling with the LCS myself. I observed that for the higher level compaction,(from
level 4 to 5) it involves much more SSTables than compacting from lower level. One compaction
could take an hour or more. By the way, you set the your SSTable size to be 100M?

Thanks.
-Wei 


________________________________
 From: Ивaн Cобoлeв <soboleiv@gmail.com>
To: user@cassandra.apache.org 
Sent: Wednesday, February 6, 2013 2:42 AM
Subject: Estimating write throughput with LeveledCompactionStrategy
 
Dear Community,

Could anyone please give me a hand with understanding what am I
missing while trying to model how LeveledCompactionStrategy works:
https://docs.google.com/spreadsheet/ccc?key=0AvNacZ0w52BydDQ3N2ZPSks2OHR1dlFmMVV4d1E2eEE#gid=0

Logs mostly contain something like this:
INFO [CompactionExecutor:2235] 2013-02-06 02:32:29,758
CompactionTask.java (line 221) Compacted to
[chunks-hf-285962-Data.db,chunks-hf-285963-Data.db,chunks-hf-285964-Data.db,chunks-hf-285965-Data.db,chunks-hf-285966-Data.db,chunks-hf-285967-Data.db,chunks-hf-285968-Data.db,chunks-hf-285969-Data.db,chunks-hf-285970-Data.db,chunks-hf-285971-Data.db,chunks-hf-285972-Data.db,chunks-hf-285973-Data.db,chunks-hf-285974-Data.db,chunks-hf-285975-Data.db,chunks-hf-285976-Data.db,chunks-hf-285977-Data.db,chunks-hf-285978-Data.db,chunks-hf-285979-Data.db,chunks-hf-285980-Data.db,].
2,255,863,073 to 1,908,460,931 (~84% of original) bytes for 36,868
keys at 14.965795MB/s.  Time: 121,614ms.

Thus spreadsheet is parameterized with throughput being 15Mb and
survivor ratio of 0.9.

1) Projected result actually differs from what I observe - what am I missing?
2) Are there any metrics on write throughput with LCS per node anyone
could possibly share?

Thank you very much in advance,
Ivan
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