Roman Naumenko wrote:
Recently I talked to a co-worker who manages NetApp storages. We discussed size
changes for pools in zfs and aggregates in NetApp.
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.
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.
And this is might be an important for corporate too. Frankly speaking I doubt there are many administrators use it in DC environment.
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.
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.
--Regards,
Roman Naumenko
ro...@naumenko.com
Expanding a RAIDZ (which, really, is the only thing that can't do right
now, w/r/t adding disks) requires the Block Pointer (BP) Rewrite
functionality before it can get implemented.
We've been promised BP rewrite for awhile, but I have no visibility as
to where development on it is in the schedule.
Fortunately, several other things also depend on BP rewrite (e.g.
shrinking a pool (removing vdevs), efficient defragmentation/compaction,
etc.).
So, while resizing a raidZ device isn't really high on the list of
things to do, the fundamental building block which would allow for it to
occur is very much important for Oracle. And, once BP rewrite is
available, I suspect that there might be a raidZ resize contribution
from one of the non-Oracle folks. Or, maybe even someone like me (whose
not a ZFS developer inside Oracle, but I play one on TV...)
Dev guys - where are we on BP rewrite?
--
Erik Trimble
Java System Support
Mailstop: usca22-123
Phone: x17195
Santa Clara, CA
Timezone: US/Pacific (GMT-0800)
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