[linux-lvm] Summary - Snapshot Effort

Greg Freemyer freemyer at NorcrossGroup.com
Wed Sep 4 14:23:01 UTC 2002

 >>  On Mon, Aug 26, 2002 at 03:10:51PM -0400, Greg Freemyer wrote:
 >>  >  >>  On Thu, Aug 22, 2002 at 05:43:42PM -0400, Greg Freemyer wrote:
 >>  >  >>  > I have not been successful at getting reliable Read-Only
 >>  snapshots
 >>  >  >>  > of XFS via LVM.  Since XFS is being used in Enterprise quality
 >>  >  >>  > applications, I suggest this is a major shortcoming that should
 >>  be
 >>  >  >>  > prioritized.
 >>  > 
 >>  >  >>  Have you tried LVM2 ?
 >>  > 
 >>  >  >>  - Joe
 >>  > 
 >>  > No I haven't.  
 >>  > 
 >>  > Instead of trying a bunch of configs myself, I have decided to write a
 >>  xfs/LVM snapshot regression module to add the xfs test suite. (They don't
 >>  have one currently.)

 >>  Yes, I read that they don't on the list.
 >>  Thanks for this effort.

 >>  > 
 >>  > Once that is done, I hope that a few different LVM configs can be
 >>  tested.  

 >>  Could you offer the regression modules and test configs on the LVM and XFS
 >>  lists so that everybody can take advantage?

This test is now in XFS cvs.

Using a current XFS CVS kernel, I have run over 1,000 iterations of the test with no errors.

FYI:  Using a xfs cvs kernel from last week, the kernel would lock up after just a few iterations.  
FYI:  Using a SuSE 8.0 kernal (XFS 1.1 release based), lvcreate would lockup after a few iterations.

====== Details
See test 068 at http://oss.sgi.com/cgi-bin/cvsweb.cgi/linux-2.4-xfs/cmd/xfstests/

It uses the fsstress executable that can be found at


It assumes there is a subdirectory of where it is run that has the fsstress executable in it.  i.e. ./src/fsstress must exist.

It currently assumes you have an existing VG (LVscratch) and that you have an existing LV (scratch) that you want to run the test against.

It will lvremove the scratch LV at the end of test, so be sure it is truly scratch.

I put in logic to have it create the PV, VG, and LV, but this is all untested and commented out with a # TODO

It also currently assumes that a few environmental variables are set before it is invoked.  This is because the XFS check routine sets them.

If you want to run it standalone, you will find the appropriate variable assignments commented out at the beginning of the file.

Last, but now least, this test should be easily modified to test any Linux FS, not just XFS.

Greg Freemyer
Internet Engineer
Deployment and Integration Specialist
Compaq ASE - Tru64 v4, v5
Compaq Master ASE - SAN Architect
The Norcross Group

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