kafka ext4文件系统的注意事项

半兽人 发表于: 2015-03-10   最后更新时间: 2016-04-09  
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kafka ext4文件系统的注意事项

Ext4 may or may not be the best filesystem for Kafka. Filesystems like XFS supposedly handle locking during fsync better. We have only tried Ext4, though.


It is not necessary to tune these settings, however those wanting to optimize performance have a few knobs that will help:


  • data=writeback: Ext4 defaults to data=ordered which puts a strong order on some writes. Kafka does not require this ordering as it does very paranoid data recovery on all unflushed log. This setting removes the ordering constraint and seems to significantly reduce latency.
    data= writeback: 默认Ext4数据=强顺序写。kafka不需要这种排序,它在未冲洗的日志来做数据恢复,这个设置取消了顺序约束,似乎大大降低了延迟。
  • Disabling journaling: Journaling is a tradeoff: it makes reboots faster after server crashes but it introduces a great deal of additional locking which adds variance to write performance. Those who don't care about reboot time and want to reduce a major source of write latency spikes can turn off journaling entirely.
  • commit=num_secs: This tunes the frequency with which ext4 commits to its metadata journal. Setting this to a lower value reduces the loss of unflushed data during a crash. Setting this to a higher value will improve throughput.
    commit=num_secs: 这个是ext4提交其元数据日志的频率,设置一个较低的值减少崩溃时未冲洗数据的丢失,这个设置较高会提高吞吐量。
  • nobh: This setting controls additional ordering guarantees when using data=writeback mode. This should be safe with Kafka as we do not depend on write ordering and improves throughput and latency.
  • delalloc: Delayed allocation means that the filesystem avoid allocating any blocks until the physical write occurs. This allows ext4 to allocate a large extent instead of smaller pages and helps ensure the data is written sequentially. This feature is great for throughput. It does seem to involve some locking in the filesystem which adds a bit of latency variance.
    delalloc: 延迟分配意味着文件系统避免分配任何块,直到物理写入发生。这允许ext4分配很大程度上代替小的页面并确保数据按顺序写入。这一特性非常适合吞吐量,它似乎涉及一些锁,在添加延迟差异的文件系统。

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