[HDFS-3120] Enable hsync and hflush by default

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.0.0-alpha
• Hadoop Flags: Reviewed
• Assignee: Eli Collins
• Reporter: Eli Collins
• Created: 21/Mar/12 01:40
• Updated: 28/Sep/15 23:58
• Resolved: 03/Apr/12 04:24

Description

The work on branch-20-append was to support sync, for durable HBase WALs, not append. The branch-20-append implementation is known to be buggy. There's been confusion about this, we often answer queries on the list like this. Unfortunately, the way to enable correct sync on branch-1 for HBase is to set dfs.support.append to true in your config, which has the side effect of enabling append (which we don't want to do).

For v1.x let's:

1. Always enable the sync path (currently only enabled if dfs.support.append is set)
2. Remove the dfs.support.append configuration option. Let's keep the code paths though in case we ever fix append on branch-1, in which case we can add the config option back

For 2.x let's

1. Always enable the hsync/hflush path
2. The dfs.support.appends only enables the append specific paths (since the hsync/hflush paths are now always on). Append will still default to being enabled so there is no net effect by default.

Issue Links

• relates to: HADOOP-8230 Enable sync by default and disable append
• relates to: HBASE-5676 Note that dfs.support.append does not have to be enabled post 1.x
• supercedes: HDFS-1107 Turn on append by default.