misc/171805: Delay during gptzfsboot

[Karli Sjöberg]

>Number:         171805
>Category:       misc
>Synopsis:       Delay during gptzfsboot
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Sep 20 07:00:24 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator:     Karli Sjöberg
>Release:        9.0
>Organization:
SLU
>Environment:
FreeBSD zfs1-1 9.0-RELEASE FreeBSD 9.0-RELEASE #0: Wed Apr 25 13:27:34 CEST 2012     admin at zfs1-1:/usr/obj/usr/src/sys/GENERIC  amd64
>Description:
The GPT ZFS-loader was recently changed from probing 4 partitions to 128 for booting, even if the disk only has two partitions... Imagine what this did to storage systems with 50 disks(or more) attached; that´s 50*128 of the delay it takes to probe at BTX.

For me, this changed the time to reboot a server to up to 20mins, while the normal time after the fix is more like 2mins. Other users at FreeBSD forums have reported delays over 10+mins as well:
https://forums.freebsd.org/showthread.php?t=31902

>How-To-Repeat:
Install FreeBSD-9.0-RELEASE with boot on ZFS
>Fix:
So, to change back this behavior:

Phase 1.
# sed -i '' 's/128/4/' /sys/boot/zfs/zfs.c

Phase 2.
Rebuild kernel/world

Phase 3.
Profit!

And booting is back to normal. This is something I always have to do with newly installed storage servers with FreeBSD-9.0-RELEASE to get back to a normal reboot time.

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