[PVFS2-users] Redundant data storage

Stuart Anderson sba at srl.caltech.edu
Thu Sep 2 14:46:31 EDT 2004


Nuts. Anyone know of any way to get there from here? There must be
a way to mirror across 2 parallel cluster filesystems?

What about SCSI Target Emulation to get linux boxes to show up
on the network as block devices? Presumably PVFS could then be
run in the more traditional fault tolerant mode where the Linux
software RAID is put underneath PVFS?


According to Rob Ross:
> Hi Stuart,
> 
> You can't do this.  Linux software RAID works with block devices, not file 
> systems.  PVFS2 does not create a large block device, it creates a large 
> file system.  So you can't build a big Linux software RAID on top of 
> PVFS2 (at least not in an obvious way).
> 
> Rob
> 
> On Thu, 2 Sep 2004, Stuart Anderson wrote:
> 
> > What about splitting my cluster in half and creating 2 100-node PVFS
> > filesystems that each node mounts as a software raid-1 device.
> > 
> > I lose half my potential storage, but will PVFS play nicely with
> > Linux software RAID so that if any one node crashes (disk and/or CPU)
> > no other node else will notice? Including the re-syncing of the
> > crashed PVFS filesystem after the node/disk are replaced and it is rebuilt?
> > 
> > According to Rob Ross:
> > > Hi Stuart,
> > > 
> > > There are plans for mirroring between servers in PVFS2, but that is 
> > > currently a research project and not something that will be deployable in 
> > > the near future.  There are also plans for a more coarse-grain ECC-based 
> > > system, but that's probably even further out.
> > > 
> > > Both of these are actually hard problems, which is why you see so many
> > > groups relying on some shared storage and failover techniques.  I don't
> > > know of anyone providing this capability in a production-quality system
> > > that could be deployed on a cluster of that size, but I'm not quite as up 
> > > on all the commercial products as I should be.
> > > 
> > > If you do find something, I'd appreciate a quick email pointing me to such 
> > > a solution :)!
> > > 
> > > Regards,
> > > 
> > > Rob
> > > 
> > > On Wed, 25 Aug 2004, Stuart Anderson wrote:
> > > 
> > > > Are there any plans for PVFS2 to support redundant storage of data at
> > > > the PVFS layer?
> > > > 
> > > > I have in mind a cluster of 200 Linux boxes with cheap internal IDE drives
> > > > that I would like to turn into a large fast shared filesystem. I understand
> > > > that if I put multiple drives in each box, or attach external shared
> > > > storage and use IP fail-over software I can obtain redundant paths to the data.
> > > > However, will PVFS2 provide any HA for single storage devices visible only
> > > > to single nodes?
> > > > 
> > > > To borrow the RAID nomenclature, if we call a simple PVFS file system RAIN-0
> > > > will PVFS2 allow RAIN-1 or possibly even RAIN-5?
> > > > 
> > > > If not, can anyone point me in the right direction for an alternative
> > > > cluster filesystem solution?
> > > > 
> > > > Thanks.
> > > > 
> > > > -- 
> > > > Stuart Anderson  sba at srl.caltech.edu  http://www.srl.caltech.edu/personnel/sba
> > > 
> > 
> > -- 
> > Stuart Anderson  sba at srl.caltech.edu  http://www.srl.caltech.edu/personnel/sba
> > 
> > 
> 

-- 
Stuart Anderson  sba at srl.caltech.edu  http://www.srl.caltech.edu/personnel/sba


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