[gpfsug-discuss] mmbackup questions

Jonathan Buzzard jonathan.buzzard at strath.ac.uk
Fri Oct 18 08:58:40 BST 2019


On 17/10/2019 19:37, Simon Thompson wrote:
> Mmbackup uses tsbuhelper internally. This is effectively a diff of
> the previous and current policy scan. Objects inspected is the count
> of these files that are changed since the last time and these are the
> candidates sent to the TSM server.
> 
> You mention not being able to upgrade a DSS-G, I thought this has
> been available for sometime as a special bid process. We did
> something very complicated with ours at one point. I also thought the
> "no-upgrade" was related to a support position from IBM on creating
> additional DAs. You can't add new storage to an DA, but believe it's
> possible and now supported (I think) to add expansion shelves into a
> new DA. (I think ESS also supports this). Note that you don't
> necessarily get the same performance of doing this as if you'd
> purchased a fully stacked system in the first place. For example if
> you initially had 166 drives as a two expansion system and then add
> 84 drives in a new expansion, you now have two DAs, one smaller than
> the other and neither the same as if you'd originally created it with
> 250 drives... I don't actually have any benchmarks to prove this, but
> it was my understanding from various discussions over time.
> 

Well it was only the beginning of this year that we asked for a quote 
for expanding our DSS-G as part of a wider storage upgrade that was to 
be put to the IT funding committee at the university. I was expecting 
just to need some more shelves, only to told we need to start again. 
Like I said if that was the case why ship with all those extra unneeded 
and unusable SAS cards and SAS cables. At the very least it is not 
environmentally friendly.

Then again the spec that came back had a 2x10Gb LOM, despite the DSS-G 
documentation being very explicit about needing a 4x1Gb LOM, which is 
still the case in the 2.4b documentation as of last month.

I do note odd numbers of shelves other than one is now supported. That 
said the tools in at least 2.1 incorrectly states having one shelf is 
unsupported!!! Presumably they the person writing the tool only tested 
for even numbers not realizing one while odd was supported. You can also 
mix shelf types now, but again if I wanted to add some SSD it's a new 
DSS-G not a couple of D1224 shelves. That also nukes the DA argument for 
no upgrades I think because you would not be wanting to mix the two in 
that way.

> There are also now both DSS (and ESS) configs with both spinning and
> SSD enclosures. I assume these aren't special bid only products
> anymore.

I don't think so, along with odd numbers of shelves they are in general 
Lenovo literature. They also have a node with NVMe up the front (or more 
accurately up the back in PCIe slots), the DSS-G100.

My take on the DSS-G is that it is a cost effective way to deploy GPFS 
storage. However there are loads of seemingly arbitrary quirks and 
limitations, a bit sh*t crazy upgrade procedure and questionable 
hardware maintenance.


JAB.

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


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