On Thu, 2007-11-01 at 08:08 -0700, Scott Spyrison wrote:
> Given 4 internal drives in a server, what kind of ZFS layout would you use? 

Assuming you needed more than one disk's worth of ZFS space after
mirroring:

disks 0+1:  partition them with a "space hog" partition at the start of
the disk followed by three more slices: 1) root#1, 2) root#2, 3) swap

Create svm mirrors for the two roots and swap.

Use live upgrade to ping-pong between roots #1 and #2.  svm mirroring
protects against disk failure; multiple roots protects against software
and administrative error.

Use the space hog partition at the start of the disk as a zfs mirror.

disks 2+3: 

mirror as a 2nd vdev in the same pool.

Future-proofing:

When the initial limited zfs boot (which will boot only from pools with
a single top-level non-raidz vdev) comes along, convert slice 1 of disks
0+1 to a zfs pool.  Migrate the system to root on that pool.  Then
expand it into slices 2 and 3 

When/if fully general zfs boot comes along (allowing boot from pools
with multiple top-level vdevs), move root into the big pool and expand
the space hog slices on disks 0 and 1 into the space formerly occupied
by the zfs root pool.  

With more disks I'd keep root separate from data pools, especially if
the data disks were external; it makes it easier to move the pool to a
different server in the event of a catastrophic failure or the
unexpected arrival of better hardware with different internal disks.
(I've had the second happen...)

                                        - Bill










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