Some questions about vfs.zfs.prefetch_disable=1 and ZFS filesystem versions
After looking at the arc_summary.pl script (found at http://jhell.googlecode.com/files/arc_summary.pl), I have realized that my system has set vfs.zfs.prefetch_disable=1 by default, looking at dmesg, I see: = ZFS NOTICE: Prefetch is disabled by default if less than 4GB of RAM is present; to enable, add vfs.zfs.prefetch_disable=0 to /boot/loader.conf. = ...except I do have 4gb of RAM. Is this caused by integrated GPU snatching some of my memory at boot? From dmesg: = real memory = 4294967296 (4096 MB) avail memory = 4088082432 (3898 MB) = What kind of things does this tunable affect and how much of a performance impact does enabling / disabling it have? Should I manually enable it? I've also noticed a really weird inconsistency, my dmesg says the following: = ZFS filesystem version 13 ZFS storage pool version 13 = Yet: = zfs get version NAME PROPERTY VALUE SOURCE cerberus version 3 - cerberus/DATA version 3 - cerberus/ROOT version 3 - cerberus/ROOT/cerberusversion 3 - cerberus/home version 3 - cerberus/home/atombsd version 3 - cerberus/home/frictionversion 3 - cerberus/home/jagoversion 3 - cerberus/home/karni version 3 - cerberus/tmp version 3 - cerberus/usr-localversion 3 - cerberus/usr-obj version 3 - cerberus/usr-portsversion 3 - cerberus/usr-ports-distfiles version 3 - cerberus/usr-src version 3 - cerberus/var version 3 - cerberus/var-db version 3 - cerberus/var-log version 3 - cerberus/var-tmp version 3 - = Is this normal or should zfs get version also show version 13? This is on a system with the pool and filesystems created with 8.0-RELEASE, by the way. Thanks! - Sincerely, Dan Naumov ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Some questions about vfs.zfs.prefetch_disable=1 and ZFS filesystem versions
Nevermind the question about ZFS filesystem versions, I should've Googled more throughly and read Pawel's responce to this question before (answer: dmesg picks the filesystem version wrong, it IS and supposed to be v3). I am still curious about prefetch though. - Sincerely, Dan Naumov ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Some questions about vfs.zfs.prefetch_disable=1 and ZFS filesystem versions
On Tue, Mar 16, 2010 at 01:40:25AM +0200, Dan Naumov wrote: After looking at the arc_summary.pl script (found at http://jhell.googlecode.com/files/arc_summary.pl), I have realized that my system has set vfs.zfs.prefetch_disable=1 by default, looking at dmesg, I see: = ZFS NOTICE: Prefetch is disabled by default if less than 4GB of RAM is present; to enable, add vfs.zfs.prefetch_disable=0 to /boot/loader.conf. = ...except I do have 4gb of RAM. Is this caused by integrated GPU snatching some of my memory at boot? From dmesg: = real memory = 4294967296 (4096 MB) avail memory = 4088082432 (3898 MB) = I've blogged about this problem when testing out 8.0-RC1. See the bottom third of my post for an explanation: http://koitsu.wordpress.com/2009/10/12/testing-out-freebsd-8-0-rc1/ The message is confusing/badly worded, despite having gone through numerous commits to change its wording. -- | Jeremy Chadwick j...@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB | ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Some questions about vfs.zfs.prefetch_disable=1 and ZFS filesystem versions
On Tue, Mar 16, 2010 at 02:06:35AM +0200, Dan Naumov wrote: Nevermind the question about ZFS filesystem versions, I should've Googled more throughly and read Pawel's responce to this question before (answer: dmesg picks the filesystem version wrong, it IS and supposed to be v3). The printing of the incorrect version number was fixed in RELENG_7 and RELENG_8 approx. 8 weeks ago. See commit revs 1.14.2.8 (RELENG_7) and 1.18.2.5 (RELENG_8) below: http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c -- | Jeremy Chadwick j...@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB | ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
