[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[
https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=14524739#comment-14524739
]
Hadoop QA commented on HDFS-4960:
-
\\
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| (x) *{color:red}-1 overall{color}* |
\\
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|| Vote || Subsystem || Runtime || Comment ||
| {color:red}-1{color} | patch | 0m 0s | The patch command could not apply
the patch during dryrun. |
\\
\\
|| Subsystem || Report/Notes ||
| Patch URL |
http://issues.apache.org/jira/secure/attachment/12591131/4960-trunk.patch |
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | trunk / f1a152c |
| Console output |
https://builds.apache.org/job/PreCommit-HDFS-Build/10583/console |
This message was automatically generated.
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 was sent by Atlassian JIRA
(v6.3.4#6332)
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[
https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13843883#comment-13843883
]
Hadoop QA commented on HDFS-4960:
-
{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12591131/4960-trunk.patch
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:red}-1 tests included{color}. The patch doesn't appear to include
any new or modified tests.
Please justify why no new tests are needed for this
patch.
Also please list what manual steps were performed to
verify this patch.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:red}-1 javadoc{color}. The javadoc tool appears to have generated
-14 warning messages.
{color:green}+1 eclipse:eclipse{color}. The patch built with
eclipse:eclipse.
{color:green}+1 findbugs{color}. The patch does not introduce any new
Findbugs (version 1.3.9) warnings.
{color:red}-1 release audit{color}. The applied patch generated 1
release audit warnings.
{color:red}-1 core tests{color}. The patch failed these unit tests in
hadoop-hdfs-project/hadoop-hdfs:
org.apache.hadoop.hdfs.server.balancer.TestBalancerWithNodeGroup
org.apache.hadoop.hdfs.web.TestWebHDFS
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-HDFS-Build/5683//testReport/
Release audit warnings:
https://builds.apache.org/job/PreCommit-HDFS-Build/5683//artifact/trunk/patchprocess/patchReleaseAuditProblems.txt
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/5683//console
This message is automatically generated.
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 was sent by Atlassian JIRA
(v6.1.4#6159)
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=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
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13705000#comment-13705000 ] Colin Patrick McCabe commented on HDFS-4960: bq. Would that cache the meta header Colin? No. We would still read it each time. bq. 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... This seems like the way to go for addressing the concerns in this JIRA. Not a huge optimization but it's easy to do. 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
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13703745#comment-13703745 ] Colin Patrick McCabe commented on HDFS-4960: Two proposals: * check the version on the DataNode side rather than the client side. Then, we don't have to re-check the header of checksum files that are already in FileInputStreamCache. * Add an optional boolean to OpRequestShortCircuitAccessProto that can be used to request *only* the block file, not the checksum file. This will avoid the overhead of duplicating the other file descriptor. In our testing, this overhead was much higher than just doing a read. Also some reminders: * if you're optimizing for SSDs (as it says in the description), seeks don't matter! * the .meta file will likely be in the cache after a few reads, so seeks won't happen anyway * let's not commit anything without at least one test that shows it's better. 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
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13703810#comment-13703810 ] Varun Sharma commented on HDFS-4960: Actually, I am currently failing to max out the SSD(s) and I am essentially looking out for things that hog CPU resources or could be time sinks. Even with this patch, i fail to max out the hardware. I will try to run an isolated test perhaps with just HDFS random seeks on the drives (no HBase). I agree that we need to have a test showing that this is really better. Currently, I doubt that it will be easy because it seems that a bunch of other paths which are hogging cpu resources. As for SSDs, seeks do matter if you are looking max them out or utilize them well enough. They obviously dont matter if you are looking at doing 10K iops. 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
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[
https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13703828#comment-13703828
]
Colin Patrick McCabe commented on HDFS-4960:
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.
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
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[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13703840#comment-13703840 ] Varun Sharma commented on HDFS-4960: IIRC, I ran with 10K or something... 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
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13702787#comment-13702787 ] Colin Patrick McCabe commented on HDFS-4960: This change seems problematic. The .meta header exists so that we can check the version of the block file. If we ignore it, we've effectively locked ourselves into a single version forever. I don't see how we can accept this change unless an alternate way of versioning the block files is also proposed. One possible way would be through the naming of the block files. But this is something we should discuss before throwing out the existing mechanism. Also, if we're going to ignore the header for no-checksum, we should ignore it in the checksum case as well. Also, did you measure the performance impact? 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
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13702832#comment-13702832 ] Varun Sharma commented on HDFS-4960: I don't know about the future plans of .meta - however, I think currently its only being used for storing checksums and if checksums are not being asked for, there is no need for seeking into the .meta file. I think the FB branch already has this change. I personally think that inlining metadata in blocks is the way to go, for the future, instead of storing separately in a .meta file - it cripples hdfs for real time work loads. I did not have a large enough data set so probably all the .meta files were in fs cache. lseek in .meta ~50 microseconds lseek in block ~50 microseconds read .meta ~50 microseconds read block ~ 300 microseconds So, just looking from system calls perspective, it is ~ 20 % however, it does not show up in the end to end test, because in general, there are a bunch of other contention issues inside HDFS + HBase which hog CPU resources. 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
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13702877#comment-13702877 ] stack commented on HDFS-4960: - bq. The .meta header exists so that we can check the version of the block file. Thanks for taking a looksee mighty [~cmccabe]. What if we made a patch with a configuration to skip the reading of metadata? Or, added a setSkipMetadata API as we have a setVerifyChecksum API? Agree, it is handy having blocks versioned so can be evolved at later date. No harm having version in side file either since we are probably going to do an extra seek to get metadata anyways (would be coolio if DN cached block metadata so could save a seek but maybe this would be more trouble than it is worth -- we'd need to prove it useful in say a heavy random read scenario). But the metadata doesn't look to have ever changed. It is version 1 (It looks like the version used to be a define out of FSDataset before it was defined inside this file but even then the version was 1). Meantime the lads here are paying a seek to learn something that is unlikely ever to change. (Filename would be good place for version but would be a massive change). Thanks Colin. 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
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[
https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13701623#comment-13701623
]
Hadoop QA commented on HDFS-4960:
-
{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12591131/4960-trunk.patch
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:red}-1 tests included{color}. The patch doesn't appear to include
any new or modified tests.
Please justify why no new tests are needed for this
patch.
Also please list what manual steps were performed to
verify this patch.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:green}+1 javadoc{color}. The javadoc tool did not generate any
warning messages.
{color:green}+1 eclipse:eclipse{color}. The patch built with
eclipse:eclipse.
{color:green}+1 findbugs{color}. The patch does not introduce any new
Findbugs (version 1.3.9) warnings.
{color:green}+1 release audit{color}. The applied patch does not increase
the total number of release audit warnings.
{color:green}+1 core tests{color}. The patch passed unit tests in
hadoop-hdfs-project/hadoop-hdfs.
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-HDFS-Build/4600//testReport/
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/4600//console
This message is automatically generated.
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
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13701670#comment-13701670 ] stack commented on HDFS-4960: - +1 on patch. When you run w/ it [~varunsharma], do you no longer see the 7-byte extra seek? All unit tests passing would seem to say you haven't broken anything. Missing I suppose is a test that shows we do not touch the .meta file at all when skip checksum is enabled (else it'd have turned up the issue you uncovered here). 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
[jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13701677#comment-13701677 ] Varun Sharma commented on HDFS-4960: Yep, that is how I confirmed it - strace now only shows lseek() into the real blocks - no more lseeks into the meta file. 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
