Storage Space: Calculating Requirements
Intended for use with Cassatt Active Response V5.0.
The Cassatt Active Response environment minimally requires
shared storage for the following:
- Cassatt Active Response base storage—contains
system software, application images, log files, and reporting data exported from the database.
- Cassatt Active Response database storage—contains
the Cassatt Active Response and reporting schema and some system configuration files.
In a high-end,
enterprise Cassatt Active Response environment featuring dual control nodes,
Cassatt Active Response accesses
this storage via the configured mount points, and a NAS or
SAN storage
solution is recommended. In a small, test or prototype environment
with
only one control node, Cassatt Active Response storage can reside on the
local disk. Either way, determining the necessary space for
Cassatt Active Response storage requires the following process:
- Determine the base storage required:
- Determine the storage required for the software running
in each Cassatt Active Response tier. (See Understanding
Cassatt Active Response: Basic Concepts for information on Cassatt Active Response
tiers.)
- Add the storage required for Cassatt Active Response
logs.
- Determine the database storage for the
Cassatt Active Response database.
I'll walk you through these steps and then show you an example.
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Determining the base storage required
To do this, you need to estimate the
number of applications you expect to run in a Cassatt Active Response tier
and the size of those application images. (This is by far
the most complicated part of this calculation.) Then
add space for log files:
Cassatt Active Response base storage formula
Cassatt Active Response base storage = (tier1_size + ...
+ tierN_size) + (logfile_size) |
This two-part calculation provides
a good estimate on the space needed for the Cassatt Active Response
base file system.
Let's do the hard part first—figure out how much
space to configure for your business applications to run in
Cassatt Active Response tiers.
Determining
space for tiers and application images
The largest component of Cassatt Active Response storage is
the image
matrix, which stores the application images running in
all the tiers in the Cassatt Active Response environment. It is important
to have sufficient space for each tier’s images; otherwise,
image capture or tier creation—key steps in bringing
applications online under Cassatt Active Response—could fail. Note
that while the Cassatt Active Response image matrix is a single view into
application images under Cassatt Active Response control, those images can
be physically distributed across multiple file systems. (Application
images can be large and quickly fill up a file system, so
if you find yourself running short of space on one file system,
it is easy to add another.)
To determine the total size
of the image matrix, calculate the space needed for each
Cassatt Active Response tier using the following formula:
Application tier formula
Tier Size = (base_image_size + (max_nodes * image_instance_size))
* number_image_versions |
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The next table describes the elements of this formula.
For this element... |
Specify... |
base_image_size |
The size of the base image. Use the
following guidelines.
For Linux, the size
of all file systems that you choose to capture on
the image host. This includes mounted SAN volumes
and NFS file systems. Use the du
-sh command to find the size of each mounted
file system on the image host.
For XenEnterprise
Hosts, determine the necessary disk
space by adding the size of the /, /rws, /tmp,
and /var partitions. To
find the sizes of these file systems, use the df
-h / /rws /tmp /var command. (Refer to the
"Used" column in the command's output.)
For Xen VM Guests, determine the necessary
disk space by adding the size of all disks configured
for the guests. This sum is the maximum size of
the base image. The actual image is compressed,
so the storage required may be less than this total,
but it's recommended to go ahead and reserve the
entire sum.
For VMware ESX Server,
determine the necessary disk space by subtracting
the size of the root file system on the image host
by the size of the VM file system (VMFS) on the image
host. To find the sizes of these file systems, use
the commands du -sh / and du
-sh /vmfs.
For Windows, determine
the necessary disk space by totaling the size of all
disks configured for the VM.
For Solaris, the size
of all file systems that you choose to capture from
the image host. This includes mounted SAN volumes
and NFS file systems. Use the du
-sh command to find the size of each mounted
file system on the image host. |
max_nodes |
The maximum number of nodes in the tier, as defined
during image capture and tier creation. |
image_instance_size |
The size of an image instance in the image matrix.
For a Linux tier, sum of sizes
of /dev, /etc, /var, /root, /tmp and
add the size of additional instance
specific directories (e.g. /home/user).
For a XenEnterprise
host tier, determine the necessary disk
space by adding the size of the /etc, /var, /root, and /tmp file
systems and the size of any additional instance
specific directories.
For a Xen
guest tier, use the base_image_size.
For a VMware ESX Server host
tier , determine the necessary disk space
by adding the sizes of /dev, /etc, /var, /root, /tmp and
the size of any additional instance
specific directories (e.g., /home/vmware).
For a Windows tier running with VMware ESX
Server, allocate 1MB of disk space.
For a Solaris tier, the size of
an image instance is the base_image_size minus
the size of /usr plus size
of any added instance
specific directories (e.g. /usr/local/share). |
number_image_versions |
Total number of versions of the image, including
the original image and any planned updates. |
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When configuring storage
for Cassatt Active Response, make sure to allocate both
enough space and enough inodes to accommodate images in the image matrix.
If there is insufficient space or number of inodes for the image matrix, Cassatt Active Response
performance will degrade. Cassatt Active Response does, however, warn you
if any of the configured storage file systems is running
short on disk space or inodes or is no longer writable.
Adding space
for log files
Once you know the space requirements
for the tiers, factor in space for Cassatt Active Response log files. By
default, logs are stored in /opt/cassatt/log.
As a general rule, use the logfile size
in the next table.
For this element... |
Specify... |
logfile_size |
10 Gbytes |
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Now, having determined the space required for each tier
and application image and factoring in the log file size,
you've got what you need to estimate required space for
the Cassatt Active Response base storage. Next, you need to figure how
much space you need for the Cassatt Active Response database.
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Determining space
for the database
The database
is stored on the Cassatt Active Response database file system specified during
the Cassatt Active Response installation. Estimate your database
size according to the next table:
For this element... |
And the configuration is... |
Specify... |
And, add the following for Cassatt Active Response reporting... |
database_size |
Small—50 nodes, 10 tiers x 5 max nodes per
tier, 20 images |
A minimum of 116.5 Mbytes. |
2.5 GB/year per 100 nodes. |
Medium—200 nodes, 20 tiers x 10 max nodes
per tier, 40 images |
A minimum of 192 Mbytes. |
Large—400 nodes, 40 tiers x 20 max nodes per
tier, 80 images |
A minimum of 348 Mbytes. |
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Example: calculating the Cassatt Active Response
base and database storage
Let's take a look
at how to apply the above formulas to estimate
Cassatt Active Response base and database storage. In this
example assume a medium sized configuration:
- 200 application nodes
- 20 tiers with max nodes equal to 10 (remember, that means
I think each tier will provide a maximum of 10 servers
for the application running in that tier)
- 40 images (let's assume 2 image updates per tier to account
new versions)
Given this configuration, you first need
to estimate space needed by your Cassatt Active Response tiers, application
images, and log files. Here's the sample calculation:
Example Cassatt Active Response base storage calculation
for Linux-based tiers
For each tier, use the
Tier Size formula:
Tier Size = (base_image_size + (max_nodes * image_instance_size))
* number_image_versions.
For the sake of example, let's assume you are running
Oracle, WebLogic, and Apache applications. Apply
that formula like this:
Oracle tier size: (7.1 Gbytes + (4 * 0.71 Gbytes) * 3 = 30 Gbytes
WebLogic tier size: (5.1 Gbytes + (7 * 0.51 Gbytes)) * 3 = 26 Gbytes
Apache tier size: (4.5 Gbytes + (20 * 0.45 Gbytes)) * 3 = 40 Gbytes
Once you have an idea about the space requirements
of the tiers and application images,
you can complete the calculation by adding space
for Cassatt Active Response log files, per the
previously discussed formula:
Cassatt Active Response base storage = (tier1_size +
... + tierN_size) + (logfile_size)
Cassatt Active Response base storage
size = (30 Gbytes + 26 Gbytes + 40 Gbytes)
+ (10 Gbytes) = 106 Gbytes |
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Using the guidelines in the database
table above, you should start with 192 Mbytes of database
space for a configuration of this size. Plus, using Cassatt Active Response Report Manager with its default settings (which run reports daily), add 2.5 Gbytes/year per 100 nodes. For the 200 nodes in the sample configuration, add 5 Gbytes. So, your minimum
required storage looks like this:
| Cassatt Active Response base storage |
106 Gbytes |
| Cassatt Active Response database storage |
5.2 Gbytes |
Example: calculating application-specific storage
If you want to extend use of your storage subsystem,
say, for example, to isolate an application on its own file
system, just loop through the application
tier formula above
to determine the space required for that application image
and tier. For instance, assuming the same configuration in
the previous example, say you want to isolate Oracle
on its own file system. Just allocate a third
storage partition of 30 Gbytes for Oracle and deduct that from the original Cassatt Active Response base
storage:
| Cassatt Active Response base storage |
81 Gbytes |
| Cassatt Active Response database storage |
5.13 Gbytes |
| Oracle application storage |
30 Gbytes |
For more information on extending use of your storage subsystem,
see Understanding Storage Management in Cassatt Active Response.
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Determining storage requirements on a large scale is never
easy. It requires understanding your immediate requirements
and your anticipated requirements. Hopefully, the formulas
I've described in this article give you a way to account
for both. In addition, and as a general guideline, it never
hurts to round up the space generously. However,
Cassatt Active Response is forgiving if you underestimate your original storage
requirements, as it is a simple matter to add capacity as
your Cassatt Active Response implementation grows.
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