[Hadoop-common-user] HDFS is corrupt, need to salvage the data.

How many Datanodes do you have.
Also, I see that your default replication is set to 1. Can you check if your datanodes are up and running.
Lohit



----- Original Message ----
From: Mayuran Yogarajah <[email protected]>
To: [email protected]
Sent: Monday, March 9, 2009 5:20:37 PM
Subject: HDFS is corrupt, need to salvage the data.

Hello, it seems the HDFS in my cluster is corrupt. This is the output from hadoop fsck:
Total size: 9196815693 B
Total dirs: 17
Total files: 157
Total blocks: 157 (avg. block size 58578443 B)
********************************
CORRUPT FILES: 157
MISSING BLOCKS: 157
MISSING SIZE: 9196815693 B
********************************
Minimally replicated blocks: 0 (0.0 %)
Over-replicated blocks: 0 (0.0 %)
Under-replicated blocks: 0 (0.0 %)
Mis-replicated blocks: 0 (0.0 %)
Default replication factor: 1
Average block replication: 0.0
Missing replicas: 0
Number of data-nodes: 1
Number of racks: 1

It seems to say that there is 1 block missing from every file that was in the cluster..

I'm not sure how to proceed so any guidance would be much appreciated. My primary
concern is recovering the data.

thanks

There is only one data node at the moment. Does this mean the data is
not recoverable?
The HD on the machine seems fine so I'm a little confused as to what
caused the HDFS to
become corrupted.

M

The block files usually don't disappear easily. Check on the datanode if
you find any files starting with "blk". Also check datanode log to see
what happened there... may be use started on a different directory or
something like that.

Raghu.

There are indeed blk files:
find -name 'blk*' | wc -l
158

I didn't see anything out of the ordinary in the datanode log.

At this point is there anything I can do to recover the files? Or do I
need to reformat
the data node and load the data in again ?

thanks

Sorry to resend this but I didn't receive a response and wanted to know
how to proceed.
Is it possible to recover the data at this stage? Or is it gone ?

thanks

Mayuran,

It takes very long for a lot of iterations if we have to go through each
debugging step, one at a time. May be a jira is a good place.

- Run fsck with blocks option.

- Check if those ids match with ids in file names found by 'find'.

- Check which directory are these files in.. and verify if that matches
with datanode configured directory

You are saying there is nothing wrong in the log files, but does it
imply that datanode sees those 157 missing blocks? May be you should
post the log or verify that yourself. If DN is working correctly
according to you, then you should not have 100% of blocks missing.

There are many possibilities, it not easy for me list the the right one
in your case without much info or list all possible conditions.

Raghu.

Mayuran Yogarajah wrote: