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Re: high performance computing, HA and RPM5

From: devzero2000 <pinto.elia@gmail.com>
Date: Mon 07 Dec 2009 - 16:56:12 CET
Message-ID: <b086760e0912070756o5a2db477mf9de4bb5040ae86@mail.gmail.com>
On Mon, Dec 7, 2009 at 4:19 PM, Jeff Johnson <n3npq@mac.com> wrote:
>
> On Dec 7, 2009, at 9:37 AM, devzero2000 wrote:
>
>> On Mon, Dec 7, 2009 at 2:55 PM, Jeff Johnson <n3npq@mac.com> wrote:
>>>
>>> On Dec 7, 2009, at 7:47 AM, devzero2000 wrote:
>>>
>>>> High performance computing systems are very popular for some time. The
>>>> problems of Hign Avalibility computer systems are common in the same
>>>> way.
>>>> The question is how a package management system as rpm5 can address
>>>> the problems of such environments. I have not found any reference to
>>>> such issues, in general systems package management system, as rpm5.
>>>> Overall this system are starting from the a simple assumption : a
>>>> single system and a single db metadata (dpkg have not a real db
>>>> however). But this assumption is wrong on a system of HPC: in general,
>>>> the applications are installed in the absence of a true package but
>>>> are installed manuallu on a file or network distributed systems: NFS,
>>>> GFS2, Luster for example. The problem, from my point of view, is that
>>>> applications are not installed using a package system like rpm5 but
>>>> installed manually: anyone thinks at this point it is sufficient to
>>>> create a virtual package with only "requires" for issue like update
>>>> conflict or the like  and it is difficult to prove the opposite: Why
>>>> should I install the same package separately on multiple nodes where
>>>> the package is the same and it is installed on the same place (on a
>>>> distributed or network filesystem). I have the opinion that a
>>>> distributed system requires a rpm5 metadata distributed database and
>>>> the fact that rpm5 includes a relational (or a sort of it in the
>>>> latest incarnation of berkeley db) database system like the model is
>>>> certainly an advantage - this what Iof a advocate  of the relational
>>>> model as Chris Date tell about this issue, last time i have checked.
>>>> On the pragmatic view, specifically, assuming the same (as patch
>>>> version) 100 nodes should be possible to extend / var / lib / rpm /
>>>> Packages  with a shared rpm5 Packages (extending _db_path for example
>>>> ) on which should be able to act as a fragment of Packages (an Union
>>>> of Packages if you like ) and if this it is unavailable, well no
>>>> problem. The preceding are only a personal opinion. There are other
>>>> opinions? I have perhaps missing something ?
>>>>
>>>
>>> HPC is usually focussed on scaling, installing identical software
>>> on many nodes efficiently.
>>>
>>> Distributing system images with modest per-node customization tends to be
>>> simpler than per-node package management. Package management is useful for
>>> constructing the system images. But PM cannot compete with system images
>>> for installation scaling to multiple nodes.
>> First of all, thanks for your reply. But i disagree on this point : it
>> would be like saying that cloning is more  useful than using conga and
>> puppet (or kickstart FWIW) and here I disagree.
>
> Well let's decompose the above statements into pieces to identify where
> we disagree.
>
> "Distributing system images ... tends to be simpler ..." and "cloning".
>        From a purely implementation POV, a package manager will always have more
>        overhead than blasting content onto physical media. The overhead introduced
>        by kernels and file systems and libraries and applications is
>        eliminated if physical images are distributed.
>
> "... modest per-node customization ... PM cannot compete" and "using conga/puppet/kickstart"
>        package != configuration management is likely the crux of the disagreement.
>        I don't believe RPM is very good at "configuration management", which
>        is better handled by kickstart or puppet or conga or Augeas. Most
>        attempts at CM in *.rpm are through scriptlets, with known deficiencies.
>        I would claim that scriptlets are the single largest cause of upgrade
>        failures today. Whether "single largest" or "one of the largest" is
>        hardly worth discussing.
>
> So I suspect we differ in package vs. configuration management assumptions.
Not like. I am pretty sure we agreed.
>
>>>
>>> Doing upgrades of multiple nodes is typically done by creating a new
>>> system image, and then undertaking a reinstallation of the new system
>>> image. This isn't as efficient as upgrading a package on a per-node basis
>>> because new system images will contain redundant already installed
>>> software. Its very hard to beat a reboot of a new system image located
>>> on a distributed file system for KISS efficiency.
>>>
>>> Tracking what system image is installed back to a specific PM database
>>> that describes the installed software within the system image could
>>> be done with a wrapper on rpm to choose 1-of-N rpmdb's to perform
>>> detailed queries re files in the system image. But a flat file manifest
>>> of what packages were installed in a system image is likely sufficient
>>> for most purposes as well.
>> But THIS make it useless or worse, the role of a package managemement
>> system, let it call call RPM5 or other.
>> Are you sure ?
>
> Not sure about anything. What I described is based on an assumption
> that physical images produced by a package manager are what could
> be distributed. What is "THIS" and why is it "useless"?
Traduzione da Italiano verso IngleseVisualizza caratteri romani
THIS, in my interpretation of your answer - wrong as it could be - is
to say a system of package management is , speaking of HPC, useless.
>
>>>
>>> A distributed PM (or system image) database using some RPC transport is
>>> fairly simple. Since installed software is slowly changing, and mostly
>> It is an opinion. Security system patch are DAILY.
>>> readonly after system images are created, the RPC performance
>>> is likely not critical. Berkeley DB supplied sunrpc until db-4.8.24. Other
>>> RPC transports onto Berkeley DB are no harder than sunrpc.
>>>
>>> The above probably (imho) describes a reasonable architecture that scales efficiently
>>> for maintaining software on most of the nodes in a HPC "cluster".
>>>
>>> There's still a need for fault tolerance on the management server(s)
>>> where images are resident and where images are produced that need
>>> more than readonly access to databases. The management servers would
>>> likely benefit from a replicated database (which Berkeley DB can
>>> provide).
>>>
>>> One can imagine an architecture using replicated databases across
>>> all nodes, with full ACID transactional properties on not only the
>>> database, but also with packages and files. But the complexity
>>> cost, and the scaling to many nodes, likely has combinatorial
>>> failures. There are other efficiencies, like multicast transport,
>>> and a reliable message bus (like dbus) that would likely be needed
>>> as well.
>> As I replied, your answer seems to reiterate that a package management
>> system is not useful in HPC ENVIRONMENT. But I do not agree. These is
>> because  a package management system involves, or is a necessary
>> substrate, for  software distribution and patch management. But the
>> your last reply it is interesting, although it deserves further
>> investigation.
>
> There's likely a further disagreement here in package vs patch management.
> The one attempt I'm aware of to integrate patch management into RPM
> (from SuSE) has been largely deprecated.
>
> I can go into details re why I believe the SuSE patch management did not
> succeed (there's nothing wrong with the patch into rpm), but basically
>        Packages as containers for immutable files is where package management "works".
> The corollary is that mutable files, either through configuration/patch management,
> or for files that aren't contained in packages, doesn't work very well with RPM.
Hu ? A package management system that not work with patches it is a
contradiction. But, i am sure, not have understood your comment. Patch
RPM, as tempted by Suse some time ago, it is largely different from
the problem i want discuss (BTW, "patch rpm" IMHO  was relative to
something that  now deltarpm solves better , for i can know ). I want
discuss only this : it is a package management system necessary in a
HPC env ? If no, it is necessary to put on ALL the system env  a
virtual provides for the "Requires" caps that the package, manually
installed because rpm is no the solution for doing this (in what i
have understood from your word), that the pkg requires ?

Best Regards
>
>>>
>>> hth random opinions from 5 minutes of thought about
>> HPC, HA, shared storage and RPM probably require further reflection.
>> IMHO  they are not been mentioned in the past is probably due to the
>> fact that many applications (user application not system) are
>> installed manually and they have not considered the benefits to use a
>> package management system for their applications
>
> Again, please take my comments as a result of 5 minutes of thought.
> There are other architectures, and additional implementations, that
> would be needed for RPM to be successful in managing HPC software
> installations.
>
> For starters, there's little reason (aside from silly 32bit constraints
> imposed on files and payloads with existing), why system image
> or network appliance or DVD or ... management could not be done in
> *.rpm. So far there's been little interest in attempting *.rpm
> extensions in those directions, largely because of the known
> 32bit limits.
In 2009 ?
>
> 73 de Jeff
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Received on Mon Dec 7 16:56:30 2009
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