Li Bo created HDFS-9826:
---------------------------
Summary: Erasure Coding: Postpone the recovery work for a
configurable time period
Key: HDFS-9826
URL: https://issues.apache.org/jira/browse/HDFS-9826
Project: Hadoop HDFS
Issue Type: Sub-task
Reporter: Li Bo
Assignee: Li Bo
Currently NameNode prepares recovering when finding an under replicated block
group. This is inefficient and reduces resources for other operations. It would
be better to postpone the recovery work for a period of time if only one
internal block is corrupted considering points shown by papers such as
\[1\]\[2\]:
1. Transient errors in which no data are lost account for more than 90% of
data center failures, owing to network partitions, software problems, or
non-disk hardware faults.
2. Although erasure codes tolerate multiple simultaneous failures, single
failures represent 99.75% of recoveries.
Different clusters may have different status, so we should allow user to
configure the time for postponing the recoveries. Proper configuration will
reduce a large proportion of unnecessary recoveries. When finding multiple
internal blocks corrupted in a block group, we do the recovery work immediately
because it’s very rare and we don’t want to increase the risk of losing data.
[1] Availability in globally distributed storage systems
http://static.usenix.org/events/osdi10/tech/full_papers/Ford.pdf
[2] Rethinking erasure codes for cloud file systems: minimizing I/O for
recovery and degraded reads
http://static.usenix.org/events/fast/tech/full_papers/Khan.pdf
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
