zfs discuss - Mar 2008 - What is likely the best way to accomplish this task?

I realize I can''t remove devices from a vdev, which, well, sucks and
all, but I''m not going to complain about that. ;)

I have 4x500G disks in a RAIDZ.  I''d like to repurpose one of them as
I''m finding that all that space isn''t really needed and that
one disk
would serve me much better elsewhere (as the second half of a mirror
in a machine going into colo).

SYS1                   124G  1.21T  29.9K  /SYS1

the only other storage in the machine is the small 60G pool made up of
the remains of the OS disks, which is not going to be enough space to
hold this all while I rebuild the array.

Is there any way that I could possibly get one of the disks out of the
pool long enough to be used as temp space while I rebuild the array with
just 3 disks?

I''m thinking either to pull it out of the machine and scribble all over
it in another machine so that it no longer has its ZFS bits on it.  If
this plan works, then it would just be a blank disk (although it will
have the same dev id, so I don''t know if zfs will pick it back up
anyway).

The other plan is to replace it with a file that resides on the 60G
partition.  This seems more likely to work, but I don''t know how
that''d
work out with the fact that the file would be a lot smaller than the
actual pool.  Maybe a thinly provisioned dev would do the trick, as I
could then make it look like 500G, but it would only really use what
it needed to resync the pool.

Is this logic all correct based on how ZFS works on snv_64a?

I could also upgrade first if that''s at all recommended, it''s
something
I''ve been meaning to do anyway.

-brian
-- 
"Perl can be fast and elegant as much as J2EE can be fast and elegant.
In the hands of a skilled artisan, it can and does happen; it''s just
that most of the shit out there is built by people who''d be better
suited to making sure that my burger is cooked thoroughly."  -- Jonathan
Patschke

On 3/4/08, Brian Hechinger <wonko at 4amlunch.net>
wrote:
>
> I realize I can''t remove devices from a vdev, which, well, sucks
and
> all, but I''m not going to complain about that. ;)
>
> I have 4x500G disks in a RAIDZ.  I''d like to repurpose one of them
as
> I''m finding that all that space isn''t really needed and
that one disk
> would serve me much better elsewhere (as the second half of a mirror
> in a machine going into colo).
>
> SYS1                   124G  1.21T  29.9K  /SYS1
>
> the only other storage in the machine is the small 60G pool made up of
> the remains of the OS disks, which is not going to be enough space to
> hold this all while I rebuild the array.
>
> Is there any way that I could possibly get one of the disks out of the
> pool long enough to be used as temp space while I rebuild the array with
> just 3 disks?
>
> I''m thinking either to pull it out of the machine and scribble all
over
> it in another machine so that it no longer has its ZFS bits on it.  If
> this plan works, then it would just be a blank disk (although it will
> have the same dev id, so I don''t know if zfs will pick it back up
anyway).
>
> The other plan is to replace it with a file that resides on the 60G
> partition.  This seems more likely to work, but I don''t know how
that''d
> work out with the fact that the file would be a lot smaller than the
> actual pool.  Maybe a thinly provisioned dev would do the trick, as I
> could then make it look like 500G, but it would only really use what
> it needed to resync the pool.
>
> Is this logic all correct based on how ZFS works on snv_64a?
>
> I could also upgrade first if that''s at all recommended,
it''s something
> I''ve been meaning to do anyway.
>
> -brian
> --
> "Perl can be fast and elegant as much as J2EE can be fast and elegant.
> In the hands of a skilled artisan, it can and does happen; it''s
just
> that most of the shit out there is built by people who''d be better
> suited to making sure that my burger is cooked thoroughly."  --
Jonathan
> Patschke
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss at opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
>

I''d suggest going the "pull one disk" route.  Stick it into
another machine,
reformat it with gparted (http://gparted-livecd.tuxfamily.org/), and
you''re
on your way.
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> have 4x500G disks in a RAIDZ.  I''d like to repurpose [...] as the
second
 > half of a mirror in a machine going into colo.

rsync or zfs send -R the 128G to the machine going to the colo

if you need more space in colo, remove one disk faulting sys1
and add (stripe) it on colo (note: you will need to destroy the pool
on colo after copying everything back to attach rather than add the
disk going to colo)

destroy and remake sys1 as 2+1 and copy it back.

removing a vdev is coming, but it will be a hole vdev, ie: remove
the 3+1 after you added a 2+1.

On Tue, Mar 04, 2008 at 09:48:05AM -0500, Rob Logan
wrote:
>  > have 4x500G disks in a RAIDZ.  I''d like to repurpose [...]
as the second
>  > half of a mirror in a machine going into colo.
> 
> rsync or zfs send -R the 128G to the machine going to the colo
Yeah, that''s the fallback plan, which I was trying to avoid, but, it
might just be the way to go.

-brian
-- 
"Perl can be fast and elegant as much as J2EE can be fast and elegant.
In the hands of a skilled artisan, it can and does happen; it''s just
that most of the shit out there is built by people who''d be better
suited to making sure that my burger is cooked thoroughly."  -- Jonathan
Patschke

> I have 4x500G disks in a RAIDZ. I''d like to repurpose one of them
> SYS1 124G 1.21T 29.9K /SYS1
This seems to be a simple task because RAID5/Z runs just fine when it is missing
one disk.  Just format one disk any way that works (take the array offline and
do it with format or zpool, or boot into a different os boot cd, etc), copy the
124gb to it from the degraded array, destroy the raidz array, create a new 3
disk array, copy the 124gb back to it, and use the single disk elsewhere.
 
 
This message posted from opensolaris.org

On Tue, Mar 04, 2008 at 09:48:05AM -0500, Rob Logan
wrote:
>  > have 4x500G disks in a RAIDZ.  I''d like to repurpose [...]
as the second
>  > half of a mirror in a machine going into colo.
> 
> rsync or zfs send -R the 128G to the machine going to the colo
And this is what I ended up doing.  So much for the "fancy" solution.
;)

-brian
-- 
"Perl can be fast and elegant as much as J2EE can be fast and elegant.
In the hands of a skilled artisan, it can and does happen; it''s just
that most of the shit out there is built by people who''d be better
suited to making sure that my burger is cooked thoroughly."  -- Jonathan
Patschke