Damien Diederen created ZOOKEEPER-4213:
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Summary: Ineffective transaction log padding on current OSes/JDKs
Key: ZOOKEEPER-4213
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-4213
Project: ZooKeeper
Issue Type: Bug
Reporter: Damien Diederen
The padding of transaction log files does not seem to result in the intended
effect, at least on Linux (JDKs 8 & 14) and macOS Catalina (JDK 8).
The files have an apparent size of ~64 MiB, as instructed, but only two blocks
are allocated:
{noformat}
$ ls -lh log.*
-rw-r--r-- 1 dash users 65M Feb 17 19:39 log.1
$ du -h --apparent-size log.*
65M log.1
$ du -h log.*
8.0K log.1
{noformat}
If the goal of log padding is to avoid filesystem allocations under load (as it
was when the ZooKeeper book was written), then sparse files are not desirable.
(This may be "minor" as it seems that nobody noticed—presumably because nobody
is running their log on spinning rust.)
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