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From C G <parallel...@yahoo.com>
Subject Re: When is HDFS really "corrupt"...(and can I upgrade a corrupt FS?)
Date Thu, 15 May 2008 19:51:55 GMT
I hadn't considered looking for the word MISSING...thanks for the heads-up.  I did a search
and found the following:
  /output/ae/_task_200803191317_9183_r_000008_1/part-00008 0, 390547 block(s):  MISSING 1
blocks of total size 0 B
0. -7099420740240431420 len=0 MISSING!

  That's the only one found.  Is it safe/sufficient to simply delete this file?  
  There were MR jobs active when the master failed...it wasn't a clean shutdown by any means.
 I surmise this file is  remnant from an active job.
  C G 
Lohit <lohit_bv@yahoo.com> wrote:
  Filesystem is considered corrupt if there are any missing blocks. do you see MISSING in
your output? and also we see missing blocks for files not closed yet. When u stopped MR cluster
where there any jobs running? 

On May 15, 2008, at 12:15 PM, C G 

Earlier this week I wrote about a master node crash and our efforts to recover from the crash.
We recovered from the crash and all systems are normal. However, I have a concern about what
fsck is reporting and what it really means for a filesystem to be marked "corrupt."

With the mapred engine shut down, I ran fsck / -files -blocks -locations to inspect the file
system. The output looks clean with the exception of this at the end of the output:

Total size: 5113667836544 B
Total blocks: 1070996 (avg. block size 4774684 B)
Total dirs: 50012
Total files: 1027089
Over-replicated blocks: 0 (0.0 %)
Under-replicated blocks: 0 (0.0 %)
Target replication factor: 3
Real replication factor: 3.0

The filesystem under path '/' is CORRUPT

In reviewing the fsck output, there are no obvious errors being reported. I see tons of output
like this:

/foo/bar/part-00005 3387058, 6308 block(s): OK
0. 4958936159429948772 len=3387058 repl=3 [,,]

and the only status ever reported is "OK."

So this begs the question about what causes HDFS to declare the FS is "corrupt" and how do
I clear this up?

The second question, assuming that I can't make the "corrupt" state go away, concerns running
an upgrade. If every file in HDFS reports "OK" but the FS reports "corrupt", is it safe to
undertake an upgrade from 0.15.x to 0.16.4 ?

Thanks for any help....

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