Does this disk/filesystem layout look sane to you?

[Dan Naumov]

The main reason for NOT using zfs directly on raw disks is the fact
that you cannot replace a vdev in a pool with a smaller one, only with
one of equal size or bigger. This leads to a problem: if you are a
regular Joe User (and not a company buying certified hardware from a
specific vendor) and want to replace one of the disks in your pool.
The new 2tb disk you buy can very often be actually a few sectors
smaller then the disk you are trying to replace, this in turn will
lead to zfs not accepting the new disk as a replacement, because it's
smaller (no matter how small).

Using zfs on partitions instead and keeping a few gb unused on each
disk leaves us with some room to play and be able to avoid this issue.


- Dan Naumov



On Mon, Jun 15, 2009 at 5:16 AM, Freddie Cash<fjwcash at gmail.com> wrote:
> I don't know for sure if it's the same on FreeBSD, but on Solaris, ZFS will
> disable the onboard disk cache if the vdevs are not whole disks.  IOW, if
> you use slices, partitions, or files, the onboard disk cache is disabled.
> This can lead to poor write performance.