Trying to clone a ZFS drive, can't get ashift=12
deischen at freebsd.org
Wed Apr 1 21:44:46 UTC 2015
On Tue, 31 Mar 2015, Peter Wemm wrote:
> 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
Thanks, and to Dmitri also. This seemed to do the trick.
It is interesting that the default in the 10.1-RELEASE
CD doesn't match the actual OS that is installed.
> 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.
The server is a web server and poudriere package builder, with some
postgres and mysql databases as backends for the web services. We
don't anticipate user data or home/project directories.
My first ZFS install was Solaris 11, which recommended (mandated?)
that rpool be from a slice not an entire disk, and boot from
an SMI (VTOC) disk. So I followed the same convention when
More information about the freebsd-stable