[gpfsug-discuss] Services on DSS/ESS nodes

[Jonathan Buzzard]

On 04/10/2020 10:29, Luis Bolinches wrote:
> Hi
> 
> As stated on the same link you can do remote mounts from each other and 
> be a supported setup.
> 
> “ You can use the remote mount feature of IBM Spectrum Scale to share 
> file system data across clusters.”
> 

You can, but imagine I have a DSS-G cluster, with 2PB of storage on it 
which is quite modest in 2020. It is now end of life and for whatever 
reason I decide I want to move to ESS instead.

What any sane storage admin want to do at this stage is set the ESS, add 
the ESS nodes to the existing cluster on the DSS-G then do a bit of 
mmadddisk/mmdeldisk and sit back while the data is seemlessly moved from 
the DSS-G to the ESS. Admittedly this might take a while :-)

Then once all the data is moved a bit of mmdelnode and bingo the storage 
has been migrated from DSS-G to ESS with zero downtime.

As that is not allowed for what I presume are commercial reasons (you 
could do it in reverse and presumable that is what IBM don't want) then 
once you are down the rabbit hole of one type of storage the you are not 
going to switch to a different one.

You need to look at it from the perspective of the users. They frankly 
could not give a monkeys what storage solution you are using. All they 
care about is having usable storage and large amounts of downtime to 
switch from one storage type to another is not really acceptable.


JAB.

-- 
Jonathan A. Buzzard                         Tel: +44141-5483420
HPC System Administrator, ARCHIE-WeSt.
University of Strathclyde, John Anderson Building, Glasgow. G4 0NG