Robert Peterson wrote:
Riaan van Niekerk wrote:
hi Bob and others
I found on the Red Hat 108 Developer Portal the following GFS1/GFS2
design document which details amongst others, some of the issues with
NFS on GFS:
https://rpeterso.108.redhat.com/servlets/ProjectDocumentView?documentID=99
(I see it was sent to this list over a year ago, but I never found it
while searching through the archives. it has a lot of good information
in it)
It has a disclaimer: Some of the comments
are no longer applicable due to design changes
My question to you or anyone who is familiar with NFS on GFS, or GFS
in general, which of the following are still valid issues for the
current (6.1u4) version of GFS. If all or most of them still apply, I
can use this as motivation for my customer to strongly consider going
off NFS on GFS. Removing the NFS from our GFS cluster has been on the
cards for quite a while, but has not gained momentum due to lack of
information on the performance gains of such a move (very difficult to
gage) or the architectural problems/limitations of NFS on GFS (for
which the following extract is spot-on).
Note - can you consider adding a link to this document from your FAQ?
Hi Riaan,
The document you mentioned was written by Ken Preslan more than a year ago.
It has some good architectural information regarding GFS and GFS2, but
the problem is, there
have been a lot of changes to GFS2 and a lot of work has been done on
NFS since that time,
so a lot of it no longer applies.
One day I was playing with 108 and decided to upload the document to my
108 page because I thought it
was "a good find" and there was a need for GFS architectural
information on the Internet.
Afterward, I was discussing the article with some of the developers and
they all agreed
that the article shouldn't be posted because it contained too much
misinformation due to recent changes
made to all areas of the code. The problem is, I had already posted the
article and I couldn't figure
out how to get 108 to delete it. (Today I figured out how to delete it,
and did so, and I apologize if
anyone was misled by what it says. I'm going to file a usability
bugzilla against 108 though.)
What I really need to do is write a white paper about GFS and its
internals and its structures,
rather than spending the time required to sift through Ken's article and
separate fact from "no longer
applicable". And the link to that document will certainly be added to
the FAQ.
There are some known issues with NFS failover, but it works great unless
you're intentionally trying to break it
by doing some nasty tricks such as those documented in bugzilla 178057.
If you read the first few comments
of the bugzilla, you'll see that I tried very hard at first to break it
and couldn't.
Wendy Cheng has been spearheading the effort to improve NFS failover and
I applaud her efforts.
Regards,
Bob Peterson
Red Hat Cluster Suite
hi Bob
I find it extremely unfortunate that you felt it necessary to remove
this article. From Wendy's reply I can deduce that most of those issues
still persist, meaning that with regards to NFS on GFS at least, the
document is still very relevant.
I know you guys are pretty busy, and I sincerely hope that you or
someone will get/make the time to write an architectural overview and
detail document of GFS, perhaps even use Ken's original document as a
base. I will gladly provide feedback on such a document, once you have
written it.
(Aside: asking a user looking for info on the innards of GFS (and this
has been asked before on the list) to settle for a cookbook on NFS on
GFS is just a long shot - with all respect).
My biggest regret is to not have saved a copy of this document locally.
It really contained quite a bit of useful information in my mind,
despite it being old and in parts deprecated.
all the best
Riaan
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