Dualboot and ZFS
Dean E. Weimer
dweimer at dweimer.net
Mon Jan 15 15:09:54 UTC 2018
On 2018-01-15 8:47 am, Victor Sudakov wrote:
> Manish Jain wrote:
>> > Sorry if my question was misleading, I did not mean converting the
>> > existing system from UFS to ZFS at ada0s3. Suppose ada0s3 is an unused
>> > slice, I can probably create a zpool thereon. But a few questions
>> > remain:
>> > 1. Can I install a root-on-zfs system on ada0s3 with bsdinstall? I
>> > suppose not?
>> That's right. You cannot install ZFS onto an MBR slice. ZFS by default
>> needs an entire disk, partitioned GPT.
> However, later you suggest it's possible to install freebsd-zfs on a
> BSD slice. How is that?
>> > Why are you creating a zpool within a BSD "a" partition, and not in
>> > da0s1 directly? I have never seen such a configuration. Is it even
>> > possible to set the "freebsd-zfs" type on a BSD partition?
>> I presume you are using MBR partitioning. Under MBR, freebsd slices
>> always nested. The slice contains partitions denoted with a, b and so
>> I do not think it is viable to set freebsd-zfs on an MBR slice. It
>> will not work. ZFS needs an entire disk. If you wish to install on an
>> MBR slice, you must use rsync after installing freebsd-UFS.
> Do you mean to say it's viable to install freebsd-zfs on ada0s3a but
> not viable on ada0s3 ? I don't see logic here.
It can be installed on a partition, but it has to be GPT, not MBR, from
one of my servers I have this GPT partition setup.
# gpart show -p
=> 40 1953525088 ada0 GPT (932G)
40 1024 ada0p1 freebsd-boot (512K)
1064 33554432 ada0p2 freebsd-swap (16G)
33555496 1919969624 ada0p3 freebsd-zfs (916G)
1953525120 8 - free - (4.0K)
ZFS is designed to use a full raw disk, but you need to have a boot
partition, and in this case I setup swap as well outside of ZFS. This
server never hits swap though, so I don't have any real world metrics on
whether or not this is better that running swap on a zvol inside of ZFS.
There is a second drive duplicating this and GEOM mirror used for the
swap, along with ZFS mirror for redundancy and a second boot partition.
Dean E. Weimer
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