Migrations and Schema CFs use disk space proportional to the square of the
number of CFs
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Key: CASSANDRA-3750
URL: https://issues.apache.org/jira/browse/CASSANDRA-3750
Project: Cassandra
Issue Type: Bug
Components: Core
Affects Versions: 1.0.1
Environment: Linux (CentOS 5.7)
Reporter: John Chakerian
Attachments: fit.png
The system keyspace grows proportional to the square of the number of CFs (more
likely, it grows quadratically with # of schema changes in general). The major
offenders in the keyspace are the Migrations table & the Schema table. On
clusters with very large #s of CFs (in the low thousands), we think that these
large system tables may be contributing to various performance issues.
The approximate expression is: s = 0.0003253*n^2 + 2.58, where n is # of
keyspaces + # of schemas and s is the size of the system keyspace in megabytes.
See attached plot of the regression curve showing fit.
Sampled data:
{noformat}
NUM_CFS SYSTEM_SIZE_IN_MB
100 4.4
200 15
300 32
400 55
500 85
600 120
700 162
800 211
900 266
1000 327
{noformat}
This was hit in 1.0.1, but is almost certainly not version specific.
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