[linux-lvm] extending striped lv

[linux-lvm] extending striped lv

[Brad Langhorst]

I read in the Howto that it is not possible to add a
disk to a striped LV.  I assume this is being worked
on - is that correct? 

What about extending an LV with free space on the same
VG? 

I've got a 2PVs in one VG and I'm planning to make an
LV that is not the whole size of the VG with the
intention of extending it later or adding a second LV
for a different purpose.  I'd like to enable striping
to realize a performance increase but only if I can
extend the LV later.

thanks!

brad



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Re: [linux-lvm] extending striped lv

[Joe Thornber]

On Thu, Aug 23, 2001 at 04:23:49PM -0700, Brad Langhorst wrote:
> I read in the Howto that it is not possible to add a
> disk to a striped LV.  I assume this is being worked
> on - is that correct? 

Not actively ATM.

- Joe

Re: [linux-lvm] extending striped lv

[Goetz Bock]

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On Thu, Aug 23 '01 at 16:23, Brad Langhorst wrote:
> [ ... extending a (striped) LV ... ]
I'm not 100% positive, but AFAIK you can extend striped LV, but if you
do the extened LV is only partially striped.
-- 
Goetz Bock                                              IT Consultant
Dipl.-Inf. Univ.

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Re: [linux-lvm] extending striped lv

[AJ Lewis]

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On Fri, Aug 24, 2001 at 11:28:59AM +0200, Goetz Bock wrote:
> On Thu, Aug 23 '01 at 16:23, Brad Langhorst wrote:
> > [ ... extending a (striped) LV ... ]
> I'm not 100% positive, but AFAIK you can extend striped LV, but if you
> do the extened LV is only partially striped.

Nope, you can only extend a striped LV on the PV's it is currently on.
After that you either have to pvmove it to larger PVs or rebuild with more
disks.

If you want to be able to extend LVs and need software striping, you might
want to consider using MD striping underneath LVM.

Regards,
-- 
AJ Lewis
Sistina Software Inc.                  Voice:  612-638-0500
1313 5th St SE, Suite 111              Fax:    612-638-0500
Minneapolis, MN 55414                  E-Mail: lewis@sistina.com
http://www.sistina.com

Current GPG fingerprint = 3B5F 6011 5216 76A5 2F6B  52A0 941E 1261 0029 2648
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Re: [linux-lvm] extending striped lv

[Jan Schreckenbach]

AJ Lewis wrote:
> Nope, you can only extend a striped LV on the PV's it is currently on.
> After that you either have to pvmove it to larger PVs or rebuild with more
> disks.
> 
> If you want to be able to extend LVs and need software striping, you might
> want to consider using MD striping underneath LVM.
> 
AJ,

does this mean I can initially build a striped LV from two smaller
disks, let me say sda and sdb and later move the LE from sda to sdc
and from sdb to sdd (where sdc and sdb a bigger than sda/sdb)? 
It is to be said that the performance of md RAID0 is somewhat better
than from striped LV's but I would prefer LVM if I could extend
a striped LV without rebuilding RAID/restoring data.

cu,
Jan

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Re: [linux-lvm] extending striped lv

[AJ Lewis]

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On Tue, Aug 28, 2001 at 12:55:40PM +0200, Jan Schreckenbach wrote:
> does this mean I can initially build a striped LV from two smaller
> disks, let me say sda and sdb and later move the LE from sda to sdc
> and from sdb to sdd (where sdc and sdb a bigger than sda/sdb)? 

Yes, that should work.  Then the LEs would be just on sdc and sdd, and sda
and sdb would be empty.

> It is to be said that the performance of md RAID0 is somewhat better
> than from striped LV's but I would prefer LVM if I could extend
> a striped LV without rebuilding RAID/restoring data.

Well, like I said, if you used md RAID0 underneath LVM, you could stripe
across, say, sda and sdb,  and then creat your LV on top of the md device,
then when you wanted to extend it, create a striped md device across sdc and
sdd and and extend the VG/LV to that md device.

Anyway, it really depends upon your application.  If you're really concerned
about speed, you'd probably go with hardware RAID0 anyway, but that's a whole
different discussion.

Regards,
-- 
AJ Lewis
Sistina Software Inc.                  Voice:  612-638-0500
1313 5th St SE, Suite 111              Fax:    612-638-0500
Minneapolis, MN 55414                  E-Mail: lewis@sistina.com
http://www.sistina.com

Current GPG fingerprint = 3B5F 6011 5216 76A5 2F6B  52A0 941E 1261 0029 2648
Get my key at: http://people.sistina.com/~lewis/gpgkey
 (Unfortunately, the PKS-type keyservers do not work with multiple sub-keys)

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