lazy mirror / live backup

Mike Wolman mike at nux.co.uk
Fri Apr 20 23:12:59 UTC 2007


According to Mike Wolman:
>> The problem with zfs is you cannot layer it as u can with the geom
>> classes.
>
>Yes and no.  It is not as versatile as all geom classes I believe but on
>FreeBSD it is a geom provider.

I havent played with zfs that much and was unaware that zfs created a 
device like the geom classes.

>> For example if you want to create a failover zfs storage pool, if you make
>> the zfs pool out of gmirror devices with one being a local device and the
>> other being a ggatec device.  You would then have your zfs raidz pool
>> replicated on a remote host.  I do not think you can do this with zfs by
>> itself as you are not able to layer raidz pool ontop of a load of zfs
>> mirrors.
>
>On plain zfs yes, you can have that.
>
>zpool create tank raidz mirror da0 da1 mirror da2 da3 mirror da4 da5.

So could you do:

zpool create rank raidz mirror ad0 ggatec0 mirror ad1 ggatec1 mirror ad2 ggatec2

Then should the primary fileserver fail would the backup machine be able 
to import this zfs pool?

Would you also be able to tune zfs to prefer the local disks to the remote 
ones?

Mike.


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