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all underlying physical volumes. You then carve space out of the volume group, creating logical volumes. On top of
a logical volume you create the file system and the mount point. You can be guided through all of these steps in the
installer, accessible by the “Create” button.
Now why would you use this complex sounding LVM at all? Because it gives you the ability to grow and
even shrink your file systems! If you are using partitions it is very difficult, if not impossible, to resize a file system.
With LVM all you need to do is extend the logical volume and resize the file system on top. This can be a life saver
if you need to upgrade Oracle and OUI complains about a lack of space.
Considerations for /u01-the Oracle mount point
The Oracle mount points have not yet been covered in this discussion. As with anything in life there is more than one
way to do it. One approach would be to keep the Oracle binaries on local storage. This means using volume group
“rootvg” or an additional, new volume group on the internal RAIDed disks with multiple logical volumes:
•
Logical volume “swaplv”
•
Logical volume “rootlv” for all Linux binaries, specifically excluding Oracle
•
Logical volume “oraclelv” for all Oracle related binaries
In environments where the Automatic Storage Management option is used you could further divide the “oraclelv”
volume into “oragridlv” and “orardbmslv” to enforce the concept of separation of duties. This subject will be covered
in more detail later in this chapter.
In addition to the local storage approach just described many sites make use of LUNs exported via a storage area
network to persist the Oracle binaries in addition to the database. Using that approach is preferred because it allows
for greater independence of the hardware. Stateless computing, which has already been mentioned in Chapter 1, is
a great way of improving a system's mean time to recovery, especially in Real Application Clusters. All that is needed
to be done is to assign the failed node's “personality” (usually an XML file) to a spare node in the chassis and boot
it up. Since it looks and feels exactly like the failed node, it can join the cluster in very little time. All of this thanks to
intelligent management tools and node-independent storage.
Regardless of whether or not you are planning on using local or SAN storage, you should set plenty of space
aside for the Oracle installation. Beginning with Oracle 11.2 the company provided point releases as full releases. The
installation process for an 11.1 RAC system begins with the installation of three software homes using the base release
11.1.0.6 software for Clusterware, ASM and the RDBMS home. That is, if you follow the white papers and install ASM
into its own software home. It is possible to start the ASM instance out of the RDBMS home as well, but in larger
environments every RDBMS patch means an ASM outage on that node too. You next had to patch each of these to the
terminal release. In the third step you finally patched all these to the latest Patch Set Update. With the full release you
can now skip the middle part and install the full release immediately. However, Oracle strongly discourages in-place
upgrades, which drive the space requirements up quite dramatically. Each new point release also seems to be very
space-demanding which leads me to the following recommendation:
•
Plan for 20GiB+ for Oracle Restart if you would like to use Oracle Automatic Storage
Management
•
Add an additional 15 GiB for each Oracle RDBMS home
Although this sounds like a lot, it is not. Each upgrade of an Oracle home will require you to store at least another
home of the same kind. The above is a conservative recommendation-compare to the Oracle 12.1 documentation
which recommends that 100GB should be made available for Grid Infrastructure alone! In addition you can remove
the old Oracle home after the successful upgrade and a sufficient grace period. Following the “disk space is cheap”
philosophy, do not be tight with disk space for Oracle installation if you can afford it.
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