[ZOOKEEPER-4213] Ineffective transaction log padding on current OSes/JDKs

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Damien Diederen
• Created: 17/Feb/21 19:07
• Updated: 17/Feb/21 19:07

Description

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:

$ 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

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.)