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From Philippe <watche...@gmail.com>
Subject Re: Scalability question
Date Mon, 15 Aug 2011 20:06:20 GMT
>
> It's another reason to avoid major / manual compactions which create a
> single big SSTable. Minor compactions keep things in buckets   which means
> newer SSTable can be compacted needing to read the bigger older tables.
>
I've never run a major/manual compaction on this ring.
In my case running repair on a "big" keyspace results in SSTables piling up.
My problematic node just filled up 483GB (yes, GB) of SSTTables. Here are
the biggest
ls -laSrh
(...)

-rw-r--r-- 1 cassandra cassandra  2.7G 2011-08-15 14:13
PUBLIC_MONTHLY_20-g-4581-Data.db

-rw-r--r-- 1 cassandra cassandra  2.7G 2011-08-15 14:52
PUBLIC_MONTHLY_20-g-4641-Data.db

-rw-r--r-- 1 cassandra cassandra  2.8G 2011-08-15 14:39
PUBLIC_MONTHLY_20-tmp-g-4878-Data.db

-rw-r--r-- 1 cassandra cassandra  2.9G 2011-08-15 15:00
PUBLIC_MONTHLY_20-g-4656-Data.db

-rw-r--r-- 1 cassandra cassandra  3.0G 2011-08-15 14:17
PUBLIC_MONTHLY_20-g-4599-Data.db

-rw-r--r-- 1 cassandra cassandra  3.0G 2011-08-15 15:11
PUBLIC_MONTHLY_20-g-4675-Data.db

-rw-r--r-- 3 cassandra cassandra  3.1G 2011-08-13 10:34
PUBLIC_MONTHLY_18-g-3861-Data.db

-rw-r--r-- 1 cassandra cassandra  3.2G 2011-08-15 14:41
PUBLIC_MONTHLY_20-tmp-g-4884-Data.db

-rw-r--r-- 1 cassandra cassandra  3.6G 2011-08-15 14:44
PUBLIC_MONTHLY_20-tmp-g-4894-Data.db

-rw-r--r-- 1 cassandra cassandra  3.8G 2011-08-15 14:56
PUBLIC_MONTHLY_20-tmp-g-4934-Data.db

-rw-r--r-- 1 cassandra cassandra  3.8G 2011-08-15 14:46
PUBLIC_MONTHLY_20-tmp-g-4905-Data.db

-rw-r--r-- 1 cassandra cassandra  4.0G 2011-08-15 14:57
PUBLIC_MONTHLY_20-tmp-g-4935-Data.db

-rw-r--r-- 3 cassandra cassandra  5.9G 2011-08-13 12:53
PUBLIC_MONTHLY_19-g-4219-Data.db

-rw-r--r-- 3 cassandra cassandra  6.0G 2011-08-13 13:57
PUBLIC_MONTHLY_20-g-4538-Data.db

-rw-r--r-- 3 cassandra cassandra   12G 2011-08-13 09:27
PUBLIC_MONTHLY_20-g-4501-Data.db

On the other nodes the same directory is around 69GB. Why are there so fewer
large files there and so many big ones on the repairing node ?
 -rw-r--r-- 1 cassandra cassandra 434M 2011-08-15 16:02
PUBLIC_MONTHLY_17-g-3525-Data.db
-rw-r--r-- 1 cassandra cassandra 456M 2011-08-15 15:50
PUBLIC_MONTHLY_19-g-4253-Data.db
-rw-r--r-- 1 cassandra cassandra 485M 2011-08-15 14:30
PUBLIC_MONTHLY_20-g-5280-Data.db
-rw-r--r-- 1 cassandra cassandra 572M 2011-08-15 15:15
PUBLIC_MONTHLY_18-g-3774-Data.db
-rw-r--r-- 2 cassandra cassandra 664M 2011-08-09 15:39
PUBLIC_MONTHLY_20-g-4893-Index.db
-rw-r--r-- 2 cassandra cassandra 811M 2011-08-11 21:27
PUBLIC_MONTHLY_16-g-2597-Data.db
-rw-r--r-- 2 cassandra cassandra 915M 2011-08-13 04:00
PUBLIC_MONTHLY_18-g-3695-Data.db
-rw-r--r-- 1 cassandra cassandra 925M 2011-08-15 03:39
PUBLIC_MONTHLY_17-g-3454-Data.db
-rw-r--r-- 1 cassandra cassandra 1.3G 2011-08-15 13:46
PUBLIC_MONTHLY_19-g-4199-Data.db
-rw-r--r-- 2 cassandra cassandra 1.5G 2011-08-10 15:37
PUBLIC_MONTHLY_17-g-3218-Data.db
-rw-r--r-- 1 cassandra cassandra 1.9G 2011-08-15 14:35
PUBLIC_MONTHLY_20-g-5281-Data.db
-rw-r--r-- 2 cassandra cassandra 2.1G 2011-08-10 16:33
PUBLIC_MONTHLY_19-g-3946-Data.db
-rw-r--r-- 2 cassandra cassandra 3.1G 2011-08-10 22:23
PUBLIC_MONTHLY_18-g-3509-Data.db
-rw-r--r-- 2 cassandra cassandra 4.0G 2011-08-10 18:18
PUBLIC_MONTHLY_20-g-5024-Data.db
-rw------- 2 cassandra cassandra 5.1G 2011-08-09 15:23
PUBLIC_MONTHLY_19-g-3847-Data.db
-rw-r--r-- 2 cassandra cassandra 9.6G 2011-08-09 15:39
PUBLIC_MONTHLY_20-g-4893-Data.db

This whole compaction thing is getting me worried : how are sites in
production dealing with SSTables becoming larger and larger and thus taking
longer and longer to compact ? Adding nodes every couple of weeks ?

Philippe

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