Date: Tue, 26 Dec 2017 18:31:05 +0100 From: "O. Hartmann" <o.hartmann@walstatt.org> To: Alan Somers <asomers@freebsd.org> Cc: Allan Jude <allanjude@freebsd.org>, FreeBSD CURRENT <freebsd-current@freebsd.org> Subject: Re: ZFS: alignment/boundary for partition type freebsd-zfs Message-ID: <20171226183132.2a6c6c2f@thor.intern.walstatt.dynvpn.de> In-Reply-To: <CAOtMX2jLKATxh0CaiesbsVGFX6ZhUmLnzvZpaQfYT0GiStJ9cw@mail.gmail.com> References: <20171226172521.611a89b0@thor.intern.walstatt.dynvpn.de> <bf2738b0-1774-af26-fd1e-151b6bd66c52@freebsd.org> <20171226180511.4d7d422e@thor.intern.walstatt.dynvpn.de> <CAOtMX2jLKATxh0CaiesbsVGFX6ZhUmLnzvZpaQfYT0GiStJ9cw@mail.gmail.com>
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[-- Attachment #1 --] Am Tue, 26 Dec 2017 10:13:09 -0700 Alan Somers <asomers@freebsd.org> schrieb: > On Tue, Dec 26, 2017 at 10:04 AM, O. Hartmann <ohartmann@walstatt.org> > wrote: > > > Am Tue, 26 Dec 2017 11:44:29 -0500 > > Allan Jude <allanjude@freebsd.org> schrieb: > > > > > On 2017-12-26 11:24, O. Hartmann wrote: > > > > Running recent CURRENT on most of our lab's boxes, I was in need to > > replace and > > > > restore a ZFS RAIDZ pool. Doing so, I was in need to partition the > > disks I was about > > > > to replace. Well, the drives in question are 4k block size drives with > > 512b emulation > > > > - as most of them today. I've created the only and sole partiton on > > each 4 TB drive > > > > via the command sequence > > > > > > > > gpart create -s GPT adaX > > > > gpart add -t freebsd-zfs -a 4k -l nameXX adaX > > > > > > > > After doing this on all drives I was about to replace, something drove > > me to check on > > > > the net and I found a lot of websites giving "advices", how to prepare > > large, modern > > > > drives for ZFS. I think the GNOP trick is not necessary any more, but > > many blogs > > > > recommend to perform > > > > > > > > gpart add -t freebsd-zfs -b 1m -a 4k -l nameXX adaX > > > > > > > > to put the partition boundary at the 1 Megabytes boundary. I didn't do > > that. My > > > > partitions all start now at block 40. > > > > > > > > My question is: will this have severe performance consequences or is > > that negligible? > > > > > > > > Since most of those websites I found via "zfs freebsd alignement" are > > from years ago, > > > > I'm a bit confused now an consideration performing all this > > days-taking resilvering > > > > process let me loose some more hair as the usual "fallout" ... > > > > > > > > Thanks in advance, > > > > > > > > Oliver > > > > > > > > > > The 1mb alignment is not required. It is just what I do to leave room > > > for the other partition types before the ZFS partition. > > > > > > However, the replacement for the GNOP hack, is separate. In addition to > > > aligning the partitions to 4k, you have to tell ZFS that the drive is 4k: > > > > > > sysctl vfs.zfs.min_auto_ashift=12 > > > > > > (2^12 = 4096) > > > > > > Before you create the pool, or add additional vdevs. > > > > > > > I didn't do the sysctl vfs.zfs.min_auto_ashift=12 :-(( when I created the > > vdev. What is > > the consequence for that for the pool? I lived under the impression that > > this is necessary > > for "native 4k" drives. > > > > How can I check what ashift is in effect for a specific vdev? > > > > It's only necessary if your drive stupidly fails to report its physical > sector size correctly, and no other FreeBSD developer has already written a > quirk for that drive. Do "zdb -l /dev/adaXXXpY" for any one of the > partitions in the ZFS raid group in question. It should print either > "ashift: 12" or "ashift: 9". > > -Alan > _______________________________________________ > freebsd-current@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" I checked as suggested and all partitions report ashift: 12. So I guess I'm save and sound and do not need to rebuild the pools ...? -- O. Hartmann Ich widerspreche der Nutzung oder Übermittlung meiner Daten für Werbezwecke oder für die Markt- oder Meinungsforschung (§ 28 Abs. 4 BDSG). [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- iLUEARMKAB0WIQQZVZMzAtwC2T/86TrS528fyFhYlAUCWkKHdAAKCRDS528fyFhY lPCeAgCM+lZW4RBGwzSNFTLLBWTATh/jI9zeMG49nlelrQjPZDaq0GUmZcUjufVN 2bmyLvYHxjk+MXfHtDi1l2s2lO2SAf9j/8T2zk0KR6iqWOLS7vOLux3JP5z0qrCU wMA0sZ4/JeHw1QU6XLHQOWbROHgF0jBUm/ktCzT/jsMcvL1p5icz =0rVe -----END PGP SIGNATURE-----help
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