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Posted to pr@cassandra.apache.org by GitBox <gi...@apache.org> on 2021/12/05 20:17:31 UTC
[GitHub] [cassandra] dpoluyanov commented on a change in pull request #1354: [16436] - Added startup check for read_ahead_kb setting.
dpoluyanov commented on a change in pull request #1354:
URL: https://github.com/apache/cassandra/pull/1354#discussion_r762609774
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File path: src/java/org/apache/cassandra/service/StartupChecks.java
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@@ -285,6 +286,49 @@ public void execute()
}
};
+ public static final StartupCheck checkReadAheadKbSetting = new StartupCheck()
+ {
+ // This value is in KB.
+ private static final long EXPECTED_READ_AHEAD_KB_SETTING = 8;
+ private static final String READ_AHEAD_KB_SETTING_PATH = "/sys/block/sda/queue/read_ahead_kb";
Review comment:
Probably should be checked not only on `sda` device, but on all data directories (not sure that it's reasonable to check `read_ahead_kb` for commit log directory)
It's common to set more than one directory in `data_file_directories` property in `cassandra.yaml`
```
data_file_directories:
- /srv/disk01
- /srv/disk02
```
`lsblk` could be used to find mount point on common hardware (and to match device name with directory)
```
$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 1.5T 0 disk /srv/disk01
sdb 8:16 0 1.5T 0 disk
`-md0 9:0 0 5.8T 0 raid0
`-md0p1 259:2 0 5.8T 0 part /srv/disk02
...
```
but pay special attention for case with software raid, where mount point could be on raid partition like on example above
software raid also could have it's own `read_ahead_kb` and makes sense to check it too.
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