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Re: Reg: Porting UFS/VxFs to ext2 (fwd)

On Thu, Nov 14, 2002 at 06:44:11PM +0530, SRIKANTH CHOWDARY M. K. G wrote:
>   The problem is that the data disks capacity is huge..infact it runs upto
> some Terra bytes. Isn't there a way to avoid backing and restoring on
> another disk? 
Not if you care about your data.  I understand the desire to do this
(having done my own strange things with moving around data on systems
without tape or networking).  But any such change is going to be quite

>  The problem will be solved if there is WRITE support to UFS/VxFS in
> linux. 
Are you talking about convertfs?


Convertfs is a very neat trick, and with a little work, could be quite
robust for converting between filesystems that are well-supported by
Linux.  But the problem of using convertfs from a migration standpoint
is that one needs robust write support to the filesystem that one is
converting from, and the more obscure the system, the less likely that
this will work.

So what to do?

If you must, I'd suggest doing the same trick as convertfs, but on the
native platform that you are migrating from.  You can create a sparse
file the size of your filesystem, and use a *userland* implementation
of ext2 to move files into that sparse fs.  [Alternatively, export
the partition using NFS or Samba, and do the file moves from a Linux
host with the sparse Linux filesystem mounted using loopback over
NFS/Samba or via [E]NBD.  This also gives you the ability to use
filesystems other than ext2/3, since you are using Linux to move
the data.]

If possible, produce a block map index file on the native platform
(using whatever BMAP-like feature is available.  If not, use the
Linux UFS filesystem in readonly-mode to do the same.  Finally, remap
the blocks, either on the native platform or on Linux.

As with convertfs, this can be done as three separate programs, and
really the only platform-specific magic is in producing the block map
index for the inode.

When you are done, kindly release it under the GPL. :-)


	Bill Rugolsky

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