[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13704848#comment-13704848 ]
stack commented on HDFS-4960: ----------------------------- bq. You could try increasing the size of the FileInputStreamCache in HDFS by setting dfs.client.read.shortcircuit.streams.cache.size to something bigger than 100. Would that cache the meta header Colin? Varun, Colin gave me crash-course offline on his option #1 above caching the meta data header for files in FileInputStreamCache; I can hack up patch when you want something to try... > Unnecessary .meta seeks even when skip checksum is true > ------------------------------------------------------- > > Key: HDFS-4960 > URL: https://issues.apache.org/jira/browse/HDFS-4960 > Project: Hadoop HDFS > Issue Type: Bug > Affects Versions: 3.0.0, 2.1.0-beta > Reporter: Varun Sharma > Assignee: Varun Sharma > Attachments: 4960-branch2.patch, 4960-trunk.patch > > > While attempting to benchmark an HBase + Hadoop 2.0 setup on SSDs, we found > unnecessary seeks into .meta files, each seek was a 7 byte read at the head > of the file - this attempts to validate the version #. Since the client is > requesting no-checksum, we should not be needing to touch the .meta file at > all. > Since the purpose of skip checksum is to also avoid the performance penalty > of the extra seek, we should not be seeking into .meta if skip checksum is > true -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira