Re: [SSI] Supporting SSI on environment not having GFS or layered CFS

[Bruce W. <br...@ka...>]

It certainly hasn't been attempted but I can't think why it
wouldn't be possibly with some work.  Some of work that
might be needed would be:
a. create a single node with SSI but with ext2 or some
	other physical filesystem for the root.
b. export the root
c. create the modified SSI kernel that can use a 
   remote root over NFS and boot that on another node.
d. For other filesystems, make sure they are mounted
   on the same mount point on all systems
e. the "reopen" code that is part of migrate should just
   work with NFS-client-open files  but hasn't been attempted 
   to my knowledge.
f. We might want to enhance the process migration to fsync
   open files before migrating, due to the much looser
   coherency guarantees of NFS.
g. Process migration while holding file locks doesn't currently
   work.  It will be fixed with GFS and CFS.  A different
   fix may be needed over NFS.
h. Interesting to see what would happen with fifos.  They
  may just work clusterwide-shared as they do in the 
  current SSI.

Some of the limitations of what the result would be:
1. Coherency would be limited to that of NFS.  Given process
   migration, the likelihood of sharing is higher so this
  is more of a restriction.
2. Basically a single root node, so availability is very
  poor.  Doing NFS to ext2 root filesystem takeover 
  would be quite an exercise.

my two cents,
   bruce

> In cluster that keeps only NFS, is the support of SSI
> possible? (process migration, clusterwide device space, etc)
>  
> -jlyu