* [linux-lvm] what use is virtualsize -- or how is it to be used?
@ 2011-07-08 5:22 Linda A. Walsh
2011-07-08 23:17 ` adultsitesoftware@gmail.com
0 siblings, 1 reply; 4+ messages in thread
From: Linda A. Walsh @ 2011-07-08 5:22 UTC (permalink / raw)
To: LVM general discussion and development
I just saw it in the man page, and first thing I tried was creating a
logical volume
by just giving a --virtualsize, arg -- thinking it would 'auto-extend
it' as needed.
Nep.
Next was looking on the net and seeing an example that gave it some
small size (-L 1G),
with a virtual size of 2G. So what is that supposed to do?
I just now thought to copy a bunch of files ( that differed from
yesterday to today) to a tmp
partition) but had it fail miserably when it REALLY failed upon reaching
the physical
limit -- not the virtual limit!)....
I was trying to use rsync to copy from a snap from yesturday of /home
that was mounted on
/ohome to 'home.diff' (the partition that I used 'virtual size' with,
... I gave it a real
size of 1G, and a virtual size of 1T.
Using rsync, I had --compare-dest=/ohome (where I mount yesturday's
snap) and copied
from /home to /home.diff (the virtual partition).... Well the diffs
were > 1G, so had
hoped /home.diff would expand to it's virtual size... Anyway, got I/O
errors, after I
ran out of space. Ok, so *that*'s not what virtual size is for...either!
Anyway, I unmounted the now 'corrupt' /home.diff, and tried to remove it...
Got all sorts of i/o errors using lvremove Home.diff. (-f didn't work
either).
Got it to remove with lvremove -f /dev/PV/Home.diff
That gave I/O errors too, but successfully completed...
So what's virtual size good for, anyway?
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [linux-lvm] what use is virtualsize -- or how is it to be used?
2011-07-08 5:22 [linux-lvm] what use is virtualsize -- or how is it to be used? Linda A. Walsh
@ 2011-07-08 23:17 ` adultsitesoftware@gmail.com
2011-07-09 0:51 ` Mike Snitzer
0 siblings, 1 reply; 4+ messages in thread
From: adultsitesoftware@gmail.com @ 2011-07-08 23:17 UTC (permalink / raw)
To: LVM general discussion and development
Virtual size lets you create a 200G file system om a 20G LV and then lvextend as needed, without the need to resize the filesystem. Read about sparse files for ideas of other uses.
It'd like a sparse device in that blocks need not actually exist until they are written to.
It currently has a performance and flexibility impact that prevents us from using it, though we would like to.
"Linda A. Walsh" <lvm@tlinx.org> wrote:
>I just saw it in the man page, and first thing I tried was creating a
>logical volume
>by just giving a --virtualsize, arg -- thinking it would 'auto-extend
>it' as needed.
>
>Nep.
>
>Next was looking on the net and seeing an example that gave it some
>small size (-L 1G),
>with a virtual size of 2G. So what is that supposed to do?
>
>I just now thought to copy a bunch of files ( that differed from
>yesterday to today) to a tmp
>partition) but had it fail miserably when it REALLY failed upon
>reaching
>the physical
>limit -- not the virtual limit!)....
>
>
>I was trying to use rsync to copy from a snap from yesturday of /home
>that was mounted on
>/ohome to 'home.diff' (the partition that I used 'virtual size' with,
>... I gave it a real
>size of 1G, and a virtual size of 1T.
>
>Using rsync, I had --compare-dest=/ohome (where I mount yesturday's
>snap) and copied
>from /home to /home.diff (the virtual partition).... Well the diffs
>were > 1G, so had
>hoped /home.diff would expand to it's virtual size... Anyway, got I/O
>errors, after I
>ran out of space. Ok, so *that*'s not what virtual size is
>for...either!
>
>Anyway, I unmounted the now 'corrupt' /home.diff, and tried to remove
>it...
>Got all sorts of i/o errors using lvremove Home.diff. (-f didn't work
>either).
>
>Got it to remove with lvremove -f /dev/PV/Home.diff
>That gave I/O errors too, but successfully completed...
>
>So what's virtual size good for, anyway?
>
>
>
>_______________________________________________
>linux-lvm mailing list
>linux-lvm@redhat.com
>https://www.redhat.com/mailman/listinfo/linux-lvm
>read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
--
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [linux-lvm] what use is virtualsize -- or how is it to be used?
2011-07-08 23:17 ` adultsitesoftware@gmail.com
@ 2011-07-09 0:51 ` Mike Snitzer
2011-07-10 17:30 ` Linda A. Walsh
0 siblings, 1 reply; 4+ messages in thread
From: Mike Snitzer @ 2011-07-09 0:51 UTC (permalink / raw)
To: LVM general discussion and development
On Fri, Jul 08 2011 at 7:17pm -0400,
adultsitesoftware@gmail.com <support@bettercgi.com> wrote:
> Virtual size lets you create a 200G file system om a 20G LV and then lvextend as needed, without the need to resize the filesystem. Read about sparse files for ideas of other uses.
>
> It'd like a sparse device in that blocks need not actually exist until they are written to.
>
> It currently has a performance and flexibility impact that prevents us from using it, though we would like to.
Please have a look at the DM thinp target that was just posted to
dm-devel.
We don't have lvm2 support for this thinp target yet, we are working on
it, but thinp is a much richer solution that should address your needs.
Mike
^ permalink raw reply [flat|nested] 4+ messages in thread
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2011-07-08 5:22 [linux-lvm] what use is virtualsize -- or how is it to be used? Linda A. Walsh
2011-07-08 23:17 ` adultsitesoftware@gmail.com
2011-07-09 0:51 ` Mike Snitzer
2011-07-10 17:30 ` Linda A. Walsh
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