[Pvfs2-users] removing storage devices

[Sam Lang]

Hi Joe,

You have a couple options.  You can just copy everything (using scp,  
tar+ssh, etc.) in the storage directory (specified in the server.conf- 
<hostname>) on the old server/raid over to one of the other nodes,  
and run two servers on that node on different ports pointing at  
different storage locations.  Once the new raid is in place you can  
copy the storage location back over.

To do this, you will have to modify the config files directly.  Each  
server has a server-specific config file (usually server.conf- 
<hostname>).  This file will have entries for the port and storage  
location.  You will need to modify both.  You'll also need to modify  
the fs.conf, so that the alias for the server you're migrating points  
to the new location.  I can give more details if this isn't clear  
enough.

Also, Ti Leggett has written a rebalancing script for redistributing  
storage after adding new servers, which isn't exactly what you're  
trying to do, but you might be able to use it for your purposes.  See:

http://www.beowulf-underground.org/pipermail/pvfs2-developers/2006- 
August/002485.html

and especially:

http://www.beowulf-underground.org/pipermail/pvfs2-developers/2006- 
September/002544.html

To redistribute onto fewer servers, you'll have to modify the fs.conf  
to _not_ specify handle ranges (for either metadata or datafiles) on  
the server you want to remove.  Keep the server alias in place  
though.  This will force new files created in the copy over to only  
be distributed on the other servers, but still allow the old files to  
be accessed from the old server.

The disadvantage here is that you're just replacing one server with  
another, so you don't benefit from the rebalance (freeing up space on  
full servers).  Unless you plan to add more than one raid/server to  
replace the old one, the first option is probably your best choice.

There's also some research being done with online migration of files  
in pvfs, but I'll let Julian comment on the details and status of  
that work.

Thanks,

-sam

On Apr 6, 2007, at 7:53 AM, Joe Georger wrote:

> Say I have a pvfs2 system using several raids as the underlying
> storage.  One of the raids is old and I want to replace it with a  
> larger
> unit.  Is there a utility that would copy all the data off that  
> raid to
> the rest of the pvfs filesystem and then let me remove it?  Or, how
> would I go about accomplishing this task?
>
> Thanks,
> Joe
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