[HADOOP-1463] dfs.datanode.du.reserved semantics being violated

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.15.3, 0.16.0
• Fix Version/s: 0.15.0
• Assignee: Hairong Kuang
• Reporter: Hairong Kuang
• Created: 05/Jun/07 18:07
• Updated: 06/Jan/11 09:07
• Resolved: 31/Jul/07 22:12

Description

Currently namenode reports two statistics back to the client:
1. The total capacity of dfs. This is a sum of all datanode's capacities, each of which is calculated by datanode summing all data directories disk space.
2. The total remaining space of dfs. This is a sum of all datanodes's remaining space. Each datanode's remaining space is calculated by using the following formula: remaining space = unused space - capacity*unusableDiskPercentage - reserved space. So the remaining space shows how much space that the dfs can still use, but it does not show the size of unused space.

Each dfs client caculates the total dfs used space by substracting remaining space from the total capacity. So the used space does not accurately shows the space that dfs is using. However it is a very important number that dfs should provide.

Issue Links

• relates to: HDFS-1564 Make dfs.datanode.du.reserved configurable per volume