Date: Wed, 10 Jul 2013 19:06:00 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: <d@delphij.net>, =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> Cc: freebsd-fs@freebsd.org, freebsd-hackers@freebsd.org, ivoras@freebsd.org Subject: Re: Make ZFS use the physical sector size when computing initial ashift Message-ID: <E22445B3685C4F3DA19A4778DB541D5E@multiplay.co.uk> References: <86zjtupz3r.fsf@nine.des.no> <51DD9801.4090808@delphij.net>
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----- Original Message -----
From: "Xin Li"
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>
> On 07/10/13 02:02, Dag-Erling Sm?rgrav wrote:
>> The attached patch causes ZFS to base the minimum transfer size for
>> a new vdev on the GEOM provider's stripesize (physical sector size)
>> rather than sectorsize (logical sector size), provided that
>> stripesize is a power of two larger than sectorsize and smaller
>> than or equal to VDEV_PAD_SIZE. This should eliminate the need for
>> ivoras@'s gnop trick when creating ZFS pools on Advanced Format
>> drives.
>
> I think there are multiple versions of this (I also have one[1]) but
> the concern is that if one creates a pool with ashift=9, and now
> ashift=12, the pool gets unimportable. So there need a way to disable
> this behavior.
I've tested my patch in all configurations I can think of including exported
ashift=9 pools being imported, all no issues.
For your example e.g.
# Create a 4K pool (min_create_ashift=4K, dev=512)
test:src> sysctl vfs.zfs.min_create_ashift
vfs.zfs.min_create_ashift: 12
test:src> mdconfig -a -t swap -s 128m -S 512 -u 0
test:src> zpool create mdpool md0
test:src> zdb mdpool | grep ashift
ashift: 12
ashift: 12
# Create a 512b pool (min_create_ashift=512, dev=512)
test:src> zpool destroy mdpool
test:src> sysctl vfs.zfs.min_create_ashift=9
vfs.zfs.min_create_ashift: 12 -> 9
test:src> zpool create mdpool md0
test:src> zdb mdpool | grep ashift
ashift: 9
ashift: 9
# Import a 512b pool (min_create_ashift=4K, dev=512)
test:src> zpool export mdpool
test:src> sysctl vfs.zfs.min_create_ashift=12
vfs.zfs.min_create_ashift: 9 -> 12
test:src> zpool import mdpool
test:src> zdb mdpool | grep ashift
ashift: 9
ashift: 9
# Create a 4K pool (min_create_ashift=512, dev=4K)
test:src> zpool destroy mdpool
test:src> mdconfig -d -u 0
test:src> mdconfig -a -t swap -s 128m -S 4096 -u 0
test:src> sysctl vfs.zfs.min_create_ashift=9
vfs.zfs.min_create_ashift: 12 -> 9
test:src> zpool create mdpool md0
test:src> zdb mdpool | grep ashift
ashift: 12
ashift: 12
# Import a 4K pool (min_create_ashift=4K, dev=4K)
test:src> zpool export mdpool
test:src> sysctl vfs.zfs.min_create_ashift=12
vfs.zfs.min_create_ashift: 9 -> 12
test:src> zpool import mdpool
test:src> zdb mdpool | grep ashift
ashift: 12
ashift: 12
> Another thing (not really related to the automatic detection) is that
> we need a way to manually override this setting from command line when
> creating the pool, this is under active discussion at Illumos mailing
> list right now.
>
> [1]
> https://github.com/trueos/trueos/commit/3d2e3a38faad8df4acf442b055c5e98ab873fb26
Yep has been on my list for a while, based on previous discussions on
zfs-devel@. I've not had any time recently but I'm following the illumos
thread to see what conclusions they come to.
Regards
Steve
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