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From Allen Wittenauer <awittena...@linkedin.com>
Subject Re: HDFS-Fuse/virtual machine images
Date Tue, 11 May 2010 15:14:45 GMT

On May 11, 2010, at 7:42 AM, Bastian Lorenz wrote:
> i have set up an hdfs cluster with three nodes(one master, two
> datanodes). Everything works fine…so far! Now i want to mount my hdfs
> with Fuse. This works also. The mountpoint is /export/hdfs. I want to
> store qcow2 files in hdfs an boot from an iso which is also stored in
> hdfs.

I expect performance to be similar to that of glaciers moving across a continent.  Last I
heard, FUSE-HDFS was a 60% performance hit over normal HDFS.

> Why i can´t store qcow2 files in hdfs? Got somebody an idea?

HDFS is not a POSIX file system, even when wrapped in FUSE.  Operations such as truncate will
NOT work:

> truncate /vm1/vm10.qcow2 12884901888
>   unique: 22, error: -95 (Operation not supported), outsize: 16

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