Date: Wed, 19 Feb 2014 17:49:54 +1030 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: "freebsd-stable@freebsd.org Stable" <freebsd-stable@freebsd.org> Subject: Separate ZIL on Root Message-ID: <743B7655-C13E-425B-96E1-A63611FBA043@gsoft.com.au>
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Hi,
I have a FreeBSD 9.2 system with 3 disks in a mirror and I am looking at adding an SSD as log & cache to improve performance.
However I have found that it will refuse to add a log dev due to..
/*
* A root pool with concatenated devices is not supported.
* Thus, can not add a device to a root pool.
*
* Intent log device can not be added to a rootpool because
* during mountroot, zil is replayed, a seperated log device
* can not be accessed during the mountroot time.
*
* l2cache and spare devices are ok to be added to a rootpool.
*/
if (spa_bootfs(spa) != 0 && nl2cache == 0 && nspares == 0) {
nvlist_free(config);
spa_close(spa, FTAG);
return (SET_ERROR(EDOM));
}
in /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c
However I don't think this is true in FreeBSD, certainly there are people working around it, eg..
http://iamsto.wordpress.com/2013/10/04/howto-freebsd-zfs-add-ssd-as-logzil-read-cache-to-root-pool/
I understand that if I lose ZIL on root then I will have a fun time recovering, although I expect this would entail a site visit and boot off a USB key and then do 'zpool import -m ...'.
So, does anyone know if there is a real problem or a hold over from Solaris?
Thanks.
--
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
-- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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