385 lines
6.8 KiB
HTML
385 lines
6.8 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML
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><HEAD
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><TITLE
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>Expanding a snapshot</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
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REL="HOME"
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TITLE="EVMS User Guide"
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HREF="index.html"><LINK
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TITLE="Creating snapshots"
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HREF="evmscreatesnap.html"><LINK
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TITLE="Reinitializing a snapshot"
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TITLE="Deleting a snapshot"
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>EVMS User Guide</TH
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 11. Creating snapshots</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="sect1"
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><H1
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CLASS="sect1"
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><A
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NAME="AEN1775"
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></A
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>11.5. Expanding a snapshot</H1
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><P
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> As mentioned in <A
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HREF="createactivsnap.html"
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>Section 11.2</A
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>, as data is
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copied from the original volume to the snapshot, the space available
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for the snapshot might fill up, causing the snapshot to be invalidated.
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This situation might cause your data backup to end prematurely, as the
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snapshot volume begins returning I/O errors after it is invalidated.
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</P
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><P
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> To solve this problem, EVMS now has the ability to expand the storage
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space for a snapshot object while the snapshot volume is active and mounted.
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This feature allows you to initially create a small snapshot object and expand
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the object as necessary as the space begins to fill up.
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</P
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><P
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> In order to expand the snapshot object, the underlying object must
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be expandable.
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Continuing the example from the previous sections, the object "snap" is
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built on the LVM region <TT
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CLASS="filename"
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>lvm/Sample Container/Sample Region</TT
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>.
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When we refer to expanding the "snap" object, the region
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<TT
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CLASS="filename"
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>lvm/Sample Container/Sample Region</TT
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> is the
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object that actually gets
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expanded, and the object "snap" simply makes use of the new space on
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that region.
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Thus, to have expandable snapshots, you will usually want to build
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your snapshot objects on top of LVM regions that have extra freespace
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available in their LVM container. DriveLink objects and some disk
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segments also work in certain situations.
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</P
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><P
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> One notable quirk about expanding snapshots is that the snapshot
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object and volume do not actually appear to expand after the operation
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is complete.
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Because the snapshot volume is supposed to be a frozen image of the original
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volume, the snapshot volume always has the same size as the original,
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even if the snapshot has been expanded.
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However, you can verify that the snapshot object is using the
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additional space by displaying the details for the snapshot object
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and comparing the percent-full field before and after the expand operation.
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</P
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><DIV
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CLASS="sect2"
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><H2
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CLASS="sect2"
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><A
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NAME="AEN1784"
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></A
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>11.5.1. Using the EVMS GUI or Ncurses</H2
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><P
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>To create the snapshot using the GUI or Ncurses, follow these steps:
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<P
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></P
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><OL
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TYPE="1"
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><LI
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><P
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>Select
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<SPAN
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CLASS="guimenu"
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>Actions</SPAN
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>-><SPAN
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CLASS="guimenuitem"
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>Expand</SPAN
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>-><SPAN
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CLASS="guimenuitem"
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>Volume</SPAN
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>
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to see a list of EVMS feature objects.
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</P
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></LI
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><LI
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><P
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>Select the volume <SPAN
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CLASS="guimenuitem"
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>/dev/evms/snap</SPAN
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>.</P
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></LI
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><LI
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><P
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>Click or activate <SPAN
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CLASS="guibutton"
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>Next</SPAN
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>.</P
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></LI
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><LI
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><P
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>Select <SPAN
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CLASS="guimenuitem"
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>lvm/Sample Container/Sample Region</SPAN
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>.
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This object is the object that will actually be expanded. </P
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></LI
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><LI
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><P
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>Click or activate <SPAN
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CLASS="guibutton"
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>Next</SPAN
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>.</P
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></LI
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><LI
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><P
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>Select the options for expanding the LVM region,
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including the amount of extra space to add to the region.
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</P
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></LI
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><LI
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><P
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>Click or activate <SPAN
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CLASS="guibutton"
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>Expand</SPAN
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>.
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</P
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></LI
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></OL
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></P
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><P
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>Alternatively, you can perform the same steps using the context sensitive menus.</P
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><P
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></P
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><OL
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TYPE="1"
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><LI
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><P
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>From the <SPAN
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CLASS="guilabel"
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>Volumes</SPAN
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> panel, right click (or press <B
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CLASS="keycap"
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>Enter</B
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> on)
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<SPAN
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CLASS="guimenuitem"
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>/dev/evms/snap</SPAN
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>.
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</P
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></LI
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><LI
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><P
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>Select <SPAN
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CLASS="guibutton"
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>Expand</SPAN
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> from the popup menu.</P
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></LI
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><LI
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><P
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>Click or activate <SPAN
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CLASS="guibutton"
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>Next</SPAN
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>.</P
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></LI
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><LI
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><P
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>Select the region <SPAN
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CLASS="guimenuitem"
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>lvm/Sample Container/Sample Region</SPAN
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>. This is the object that will
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actually be expanded.</P
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></LI
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><LI
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><P
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>Click or activate <SPAN
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CLASS="guibutton"
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>Next</SPAN
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>.</P
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></LI
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><LI
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><P
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>Select the options for expanding the LVM region, including the
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amount of extra space to add to the region.</P
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></LI
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><LI
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><P
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>Click or activate <SPAN
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CLASS="guibutton"
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>Expand</SPAN
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>.</P
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></LI
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></OL
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></DIV
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><DIV
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CLASS="sect2"
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><H2
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CLASS="sect2"
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><A
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NAME="AEN1835"
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></A
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>11.5.2. Using the CLI</H2
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><P
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>The CLI expands volumes by targeting the object to be
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expanded.
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The CLI automatically handles expanding the volume and other objects above the volume
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in the volume stock. As with a regular expand operation, the options are determined
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by the plug-in that owns the object being expanded.</P
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><P
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>Issue the following command to determine the expand options for the
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region <TT
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CLASS="filename"
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>lvm/Sample Container/Sample Region</TT
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>:</P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><FONT
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COLOR="#000000"
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><PRE
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CLASS="programlisting"
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>query:region,region="lvm/Sample Container/Sample Region",lo</PRE
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></FONT
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></TD
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></TR
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></TABLE
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><P
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>The option to use for expanding this region is called "add_size."
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Issue the following command to expand the snapshot by 100 MB:</P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><FONT
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COLOR="#000000"
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><PRE
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CLASS="programlisting"
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>expand:"lvm/Sample Container/Sample Region", add_size=100MB</PRE
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></FONT
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></TD
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></TR
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></TABLE
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>Prev</A
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>Reinitializing a snapshot</TD
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WIDTH="34%"
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ALIGN="center"
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