kern/98749: NFS and QUOTA are bad bedfellows?

[Joe Greco]

>Number:         98749
>Category:       kern
>Synopsis:       NFS and QUOTA are bad bedfellows?
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Jun 09 13:00:46 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator:     Joe Greco <jm+freebsd-pr at ns.sol.net>
>Release:        FreeBSD 6.1-RELEASE amd64
>Organization:
sol.net Network Services - Solaria Public Access UNIX
>Environment:
System: 6.1-RELEASE FreeBSD 6.1-RELEASE #1: Fri Jun  9 07:22:01 CDT 2006 amd64

The server in question is a Tyan S2882 with 512MB, an Opteron OSB240 CPU,
and a 3Ware 9550SX-4LP RAID controller, with four drives in a RAID5 config.
Its primary function is as an NFS server.

>Description:
	We've been using NFS to support our shell server for many years,
	now.  It is nice for numerous reasons, perhaps primarily because
	it gives us a huge amount of control over the access that users
	actually have to the system files.

	Our old NFS server (4.* based) was recently replaced by a new
	server, which mandated the use of 6.1R so that we could have
	driver support for the new 9550.  

	We have been experiencing massive performance problems compared
	to the old 4.* server; many I/O intensive operations would proceed
	slowly while making the NFS server completely unresponsive at the
	command line (run "top", set to s1, set prio high, and then on the
	shell box use mutt to load a large mailbox file, it'd just *stop*)
	
	This is obviously somewhat annoying.

	Upon further examination, it appears that there is a bad interaction
	of some sort when using "options QUOTA".  Removing it from the
	server's kernel configuration made things run reasonably fast, but,
	for obvious reasons, this is undesirable for normal operations.

>How-To-Repeat:
	Enable "options QUOTA" on a FreeBSD 6.1R/amd64 server, configure
	some quotas on an exported filesystem, and then generate some NFS
	I/O load on that filesystem, while monitoring top or other perf
	tools on the server.

>Fix:

	No fix; workaround is to remove "options QUOTA"


>Release-Note:
>Audit-Trail:
>Unformatted: