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List:       evms-devel
Subject:    Re: [Evms-devel] expand / shrink question
From:       Frank Lenaerts <lenaerts.frank () pandora ! be>
Date:       2002-08-07 12:50:43
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on Tue, Aug 06, 2002 at 05:46:26PM -0400, Mark Peloquin wrote about Re: [Evms-devel] \
expand / shrink question:

Just some feedback.

> > I created the following setup: 2 segments (5GB) sda1 and sdb1 are
> > mirrored (RAID1) and result in md/md0, volume v1 is a native EVMS
> > volume and is created from md/md0; created an ext3 filesystem on the
> > volume:
> 
> > v1 -> md0 -> sda1 & sdb1
> 
> This is not a good example volume to test expand and shrink
> capabilities. RAID1 arrays by nature (at least the MD way)
> are not expandable or shrinkable. The same is true for RAID5.
> I'm not saying this isn't theoritically possible, just the
> MD implementation does not and has never supported such
> operations. Bear in mind EVMS currently follows the MD
> implementation in these regards.

Ok, nice to know. Indeed, doing EVMS: q:SP,/dev/evms/v1 does not
present any shrink points.

> Expansion can happen in multiple ways. One is the volume is
> produced by an aggregator (such as drivelink, LVM, MD-linear,
> AIX, or OS/2). In these cases, the volumes could be expanded
> by adding a new element to the volume, OR it could be expanded by
> expanding the size of the final object in the volume. Likewise
> shrinking could happen by removing objects or shrinking the
> endmost object.

I now created the following situation:

c:s,sdc_freespace1,size=100MB
c:v,sdc1,n="v2"

EVMS: q:v,Expandable    

Volume Name: /dev/evms/hda8
Volume Size: 1.86 GB
Minor Number: 6
This volume is not mounted.
 ---------> uhh? This compatibility volume _is_ mounted!
Filesystem: Ext2/3
Max Filesystem Size: 16.00 TB
Min Filesystem Size: 62.05 MB

Volume Name: /dev/evms/v2
Volume Size: 99.98 MB
Minor Number: 254
This volume is not mounted.
Filesystem: Ext2/3
Max Filesystem Size: 4.00 TB
Min Filesystem Size: 7.20 MB

# try to expand the volume
EVMS: e:/dev/evms/v2,size=200MB,sdc_freespace1


A command line parameter was out of range!

# try to shrink the volume
EVMS: S:/dev/evms/v2,size=60MB,/dev/evms/v2


A command line parameter was out of range!

# used evmsgui to try to do the same and it worked there; first of
# all, when selecting the volume, I could see that the shrinkpoint was
# actually sdc1 and then the Messages dialog shows that it actually
# uses resize2fs on sdc1.

# try to do the same in the CLI
EVMS: e:sdc1,size=200MB,sdc_freespace1


Ext2/3: expand output:



Ext2/3: resize2fs 1.27 (8-Mar-2002)




Ext2/3: The filesystem on /dev/evms/v2 is now 307183 blocks long.

# so, to actually resize a volume, you are resizing the segment (in
# this case at least, where a volume is mapped directly to a segment)

# you have to use q:SP,/dev/evms/v2 to determine the shrink points for
# a volume (instead of q:v,Shrinkable)

EVMS: q:SP,/dev/evms/v2

Segment Name: sdc1
Segment Size: 99.98 MB
Starting LBA: 32
Segment Type: Data


BTW: Isn't it possible to add a QUIT command to the evms CLI?
Certainly now that the CLI seems to have readline support, I often
quit the CLI accidentally. An explicit quit command, as in the GUI ;-)
would be nice. 

-- 
lenaerts.frank@pandora.be

Those who do not understand Unix are condemned to reinvent it, poorly."
-- Henry Spencer


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