zfs on gmirror slice

[Mark Stapper]

Miroslav Lachman wrote:
> Maciej Jan Broniarz wrote:
>> 2009/9/1 Thomas Backman <serenity at exscape.org>:
>>
>>> On Sep 1, 2009, at 4:04 PM, Maciej Jan Broniarz wrote:
>>>
>>>
>>> I'm not familiar with gmirror, but it'd be a way better idea to
>>> mirror it
>>> using ZFS if possible - that way you get self-healing and stuff like
>>> that,
>>> which you won't if ZFS doesn't have a mirror/RAIDZ setup, but only
>>> sees a
>>> single slice.
>>>
>>
>>
>> I would like to do so. I have to disks (ad4 and ad5). Is it possible
>> to create two slices on both disks (eg ad4s1 and ad4s2 for ad4).
>> Then to create gmirror on ad4s1, install freebsd on it so it would
>> boot from it. Then, after having my system running to create zfs
>> mirror from ad4s2 and ad5s2?
>
> Yes, I am using it this way:
>
> root at cage ~/# gmirror status
>        Name    Status  Components
> mirror/gms1  COMPLETE  ad4s1
>                        ad6s1
>
>
> root at cage ~/# zpool status
>   pool: tank
>  state: ONLINE
>  scrub: none requested
> config:
>
>         NAME        STATE     READ WRITE CKSUM
>         tank        ONLINE       0     0     0
>           mirror    ONLINE       0     0     0
>             ad4s2   ONLINE       0     0     0
>             ad6s2   ONLINE       0     0     0
>
> errors: No known data errors
>
>
> root at cage ~/# zpool list
> NAME                    SIZE    USED   AVAIL    CAP  HEALTH     ALTROOT
> tank                    444G    353G   91.2G    79%  ONLINE     -
>
>
> gmirror gms1 is for system files, ports etc. zpool (444GB) is for jails
>
> Miroslav Lachman
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Hello,

I'm quite surprised by your setup, as you are using two mechanisms to
accomplish the exact same thing: data replication.
If you want two slices of toast do you use a toaster for one, and an
oven for the other?
My advice to you: either use zfs or gmirror to realize redundancy.
Of course, zfs provides far more flexibility then UFS. However, as
mentioned, booting from ZFS isn't something sysinstall can setup for you.
Besides, updating a zfs filesystem which you are running from is next to
impossible. And since ZFS is still under heavy development, you will
want to update your zfs version every now and then.
So, i would recommend setting up gmirror to mirror your whole disks,
install the base system(boot and "world") on a small UFS slice, and use
the rest of the disc as zfs slice.
If you feel comfortable enough running your entire system on zfs, you
could use a mirrored zpool to boot from. Takes a little more efford, but
is more uniform.
Updating zfs will be a pain though. You would have to boot from another
filesystem to be able to update your root filesystem.
If you'll be reinstalling your system, you might want to check out
FreeBSD 8 because zfs boot support is better.
Hope it helps.
Greetz,
Mark


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