[OpenAFS] AFS namei file servers, SAN, any issues elsewhere? We've had some. Can AFS _cause_ SAN issues?

Jason Edgecombe jason@rampaginggeek.com
Wed, 19 Mar 2008 20:56:32 -0400

Is this what you need?

      NAME:  SAN Foundation Kit
  CATEGORY:  system
      ARCH:  sparc
   VERSION:  1.0
   BASEDIR:  /
    VENDOR:  Sun Microsystems, Inc.
      DESC:  This package provides a support for the SAN Foundation Kit.
    PSTAMP:  sanserve-a20031029172438
  INSTDATE:  Jan 15 2008 10:37
   HOTLINE:  Please contact your local service provider
    STATUS:  completely installed
     FILES:       22 installed pathnames
                   4 shared pathnames
                   1 linked files
                  11 directories
                   2 executables
                 239 blocks used (approx)

Running Solaris 9 09/05HW Sparc with Sun SAN foundation.


Kim Kimball wrote:
> Hi Jason,
> Thanks!
> Can you tell me which flavor of SAN you're using?
> Kim
> Jason Edgecombe wrote:
>> Robert Banz wrote:
>>> AFS can't really cause "san issues" in that it's just another 
>>> application using your filesystem.  In some cases, it can be quite a 
>>> heavy user of such, but since its only interacting through the fs, 
>>> its not going to know anything about your underlying storage fabric, 
>>> or have any way of targeting it for any more badness than any other 
>>> filesystem user.
>>> One of the big differences that would effect the filesystem IO load 
>>> that occurred between 1.4.1 & 1.4.6 was the removal functions that 
>>> made copious fsync operations.  These operations were called in 
>>> fileserver/volserver functions that modified various in-volume 
>>> structures, specifically file creations and deletions, and would 
>>> lead to rather underwhelming performance when doing vos restores, 
>>> deleting, or copying large file trees.  In many configurations, this 
>>> causes the OS to pass on a call to the underlying storage to verify 
>>> that all changes written have been written to *disk*, causing the 
>>> storage controller to flush its write cache.  Since this defeats 
>>> many of the benefits (wrt I/O scheduling) on your storage hardware 
>>> of having a cache, this could lead to overloaded storage.
>>> Some storage devices have the option to ignore these calls from 
>>> devices, assuming your write cache is reliable.
>>> Under UFS, I would suggest that you'd be running in 'logging' mode 
>>> when using the namei fileserver on Solaris, as yes, fsck is rather 
>>> horrible to run.  Performance on reasonably recent versions of ZFS 
>>> were quite acceptable as well.
>> I can confirm Robert's observations. I recently tested openafs 1.4.1 
>> inode vs 1.4.6 namei on solaris 9 sparc with a Sun Storedge 3511 
>> Expansion tray fibre channel device. The difference is stagerring 
>> with vos move and such. We have been using the 1.4.6 namei config on 
>> a SAN for a few months now with no issues.
>> Jason
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