Date: Tue, 31 Mar 2015 23:31:47 -0700 From: Peter Wemm <peter@wemm.org> To: freebsd-stable@freebsd.org, Daniel Eischen <deischen@freebsd.org> Subject: Re: Trying to clone a ZFS drive, can't get ashift=12 Message-ID: <2588497.o59NqK340E@overcee.wemm.org> In-Reply-To: <Pine.GSO.4.64.1504010016170.26089@sea.ntplx.net> References: <Pine.GSO.4.64.1504010016170.26089@sea.ntplx.net>
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On Wednesday, April 01, 2015 12:30:46 AM Daniel Eischen wrote: > I have an Oracle (nee Sun) X4-2 server with identical 300GB SAS > drives. I did an MBR ZFS install from FreeBSD 10.1-RELEASE CD > and have it updated to p6: [..] > # zpool create -o cachefile=/tmp/newpool.cache bootpoolNew label/boot0 > # zdb -U /tmp/newpool.cache | grep ashift > ashift: 9 > > What gives? How do I get it to use 4k? Before creating the pool, try: # sysctl vfs.zfs.min_auto_ashift=12 But watch your alignment of the MBR slices/partitions. I think you'll find it easier to manage with gpt for a data disk, eg: # gpart create -s gpt da1 # gpart add -t freebsd-zfs -a 4k da1 combine that with the sysctl above you should have everything on 4k. Setting -a just sets the rounding for the start/end sectors, it doesn't affect zfs when its sizing the sector size internally. btw; for a 300G drive you might not want 4k - this changes the base allocation size to be 8 times larger. You might find your space efficiency less than ideal if you have a lot of tiny files. -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV UTF-8: for when a ' or ... just won\342\200\231t do\342\200\246
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