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From Aaron Kimball <aa...@cloudera.com>
Subject Re: input/output error while setting up superblock
Date Fri, 22 May 2009 18:09:58 GMT
More specifically:

HDFS does not support operations such as opening a file for write/append
after it has already been closed, or seeking to a new location in a writer.
You can only write files linearly; all other operations will return a "not
supported" error.

You'll also find that random-access read performance, while implemented, is
not particularly high-throughput. For serving Xen images even in read-only
mode, you'll likely have much better luck with a different FS.

- Aaron


2009/5/22 Taeho Kang <tkang1@gmail.com>

> I don't think HDFS is a good place to store your Xen image file as it will
> likely be updated/appended frequently in small blocks. With the way HDFS is
> designed for, you can't quite use it like a regular filesystem (e.g. ones
> that support frequent small block appends/updates in files). My suggestion
> is to use another filesystem like NAS or SAN.
>
> /Taeho
>
> 2009/5/22 신승엽 <mikasa83@naver.com>
>
> > Hi, I have a problem to use hdfs.
> >
> > I mounted hdfs using fuse-dfs.
> >
> > I created a dummy file for 'Xen' in hdfs and then formated the dummy file
> > using 'mke2fs'.
> >
> > But the operation was faced error. The error message is as follows.
> >
> > [root@localhost hdfs]# mke2fs -j -F ./file_dumy
> > mke2fs 1.40.2 (12-Jul-2007)
> > ./file_dumy: Input/output error while setting up superblock
> > Also, I copyed an image file of xen to hdfs. But Xen couldn't the image
> > files in hdfs.
> >
> > root@localhost hdfs]# fdisk -l fedora6_demo.img
> > last_lba(): I don't know how to handle files with mode 81a4
> > You must set cylinders.
> > You can do this from the extra functions menu.
> >
> > Disk fedora6_demo.img: 0 MB, 0 bytes
> > 255 heads, 63 sectors/track, 0 cylinders
> > Units = cylinders of 16065 * 512 = 8225280 bytes
> >
> >           Device Boot      Start         End      Blocks   Id  System
> > fedora6_demo.img1   *           1         156     1253038+  83  Linux
> >
> > Could you answer me anything about this problem.
> >
> > Thank you.
> >
>

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