Brandon High said the following, on 06/02/2010 11:47 PM:
On Wed, Jun 2, 2010 at 3:54 PM, Roman Naumenko<ro...@naumenko.ca> wrote:
And some time before I had suggested to a my buddy zfs for his new home storage
server, but he turned it down since there is no expansion available for a pool.
There's no expansion for aggregates in OnTap, either. You can add more
disks (as a raid-dp or mirror set) to an existing aggr, but you can
also add more vdevs (as raidz or mirrors) to a zpool two.
I think there is a difference. Just quickly checked netapp site:
Adding new disks to a RAID group If a volume has more than one RAID
group, you can specify the RAID group to which you are adding disks.
To add new disks to a specific RAID group of a volume, complete the
following step.
Example
The following command adds two disks to RAID group 0 of the vol0 volume:
vol add vol0 -g rg0 2
You can obviously add disks just to a raid group as well.
And he really wants to be able to add a drive or couple to an existing pool.
Yes, there are ways to expand storage to some extent without rebuilding it.
Like replacing disk with larger ones. Not enough for a typical home user I
would say.
You can do this. 'zpool add'
Nevertheless, NetApp appears to have such feature as I learned from my
co-worker. It works with some restrictions (you have to zero disks before
adding, and rebalance the aggregate after and still without perfect
distribution) - but Ontap is able to do aggregates expansion nevertheless.
Yeah, you can add to a aggr, but you can't add to a raid-dp set. It's
the same as ZFS.
ZFS doesn't require that you zero disks, and there is no rebalancing.
As more data is written to the pool it will become more balanced
however.
So, my question is: what does prevent to introduce the same for zfs at present
time? Is this because of the design of zfs, or there is simply no demand for it
in community?
My understanding is that at present time there are no plans to introduce it.
Rebalancing depends on bp_rewrite, which is vaporware still. There has
been discussion of it for a while but no implementation that I know
of.
Once the feature is added, it will be possible to add or remove
devices from a zpool or vdev, something that OnTap can't do.
But are there any plans to implement it?
--Roman
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