STAT Utility and Storwize V7000

IBM Storwize V7000 and Easy Tier™

© Copyright IBM Corporation, 2011 ____________________________________________________________________

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Using the Storage Tier Advisor Tool (STAT) and Easy TierTM on the IBM Storwize V7000

Gonzalo Fuentes

Dan Riedel

William Wiegand

IBM System and Technology Group / IBM Advanced Technical Skills

February 3, 2011



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The IBM Storwize V7000 incorporates some of IBM’s top technologies, typically found only in

enterprise-class storage systems, raising the standard for storage efficiency in midrange disk systems.

One of the interesting features on the Storwize V7000 is an automated data migration process known as

Easy Tier™

. The Easy Tier™

function continuously measures data access patterns and will automatically

migrate high activity “hot” spots from Hard Disk Drives (HDDs) to Solid State Drives (SSDs). The

Easy Tier™

function, included in the base software license, gives customers an easy to use method for

increasing the cost effectiveness of their disk storage technology.

In conjunction with the Easy Tier™

function, IBM has also developed a utility called the Storage Tier

Advisor Tool (STAT) that can be used to interpret historical usage information from DS8K, SVC or

Storwize V7000 storage systems. It can help determine what if any benefit could be gained by adding

SSDs to the system prior to actually investing in them.

The IBM STAT utility provides information on how much value can be derived by placing “hot” data

with high I/O density and low response time requirements on SSDs while targeting HDDs for “cooler”

data that is accessed more often sequentially and at lower I/O rates.

The objective of this paper is to show the reader how to perform the following activities:

1) Activate the Easy Tier™

measurement capability on a storage pool to generate the heat map data

file to be used with the STAT utility.

2) Execute the STAT utility to obtain HTML reports showing the potential benefit of adding SSDs.

3) Define a RAID-5 SSD array/Managed Disk (MDisk) and add it to the measured storage pool.

4) Collect another heat map data file to use with the STAT utility again to show how the SSD

storage is now populated with all the “hot” extents identified by Easy Tier™

.

5) Show graphically the dramatic performance benefits possible having Easy Tier™

automatically

provide the right storage tier for the specific application data being accessed most often.



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Storwize V7000:

The test configuration was a Storwize V7000 (1 Control enclosure and 4 Expansion enclosures) with a

total of 114 SAS drives (300GB 10K RPM each) running software version 6.1.0.5.

AIX SYSTEM:

System Model: IBM 9117-MMA

Processor Implementation Mode: POWER 6

Number of Processors: 4

Processor Clock Speed: 4704 MHz

CPU Type: 64-bit

Kernel Type: 64-bit

Memory Size: 8448 MB

Host Bus Adapters: Emulex 4 GB



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A storage pool named “INTERNAL_POOL” was populated with Storwize V7000 internal MDisks and a

100GB Volume was carved from it and allocated to the AIX system which was running the IORATE

workload generation tool. The host workload focused on creating 8K random read I/O in an area that

represented 20% of the Volume (20GB) so these extents would become flagged as “hot” spots by Easy

Tier™

. This would allow them to be promoted to SSD storage when available.

The storage pool currently has HDDs in it, so by default it does not have Easy Tier™

measurement

enabled to collect the data the STAT utility requires, this must be manually enabled.

To activate the Easy Tier™

function on the “INTERNAL_POOL” (MDG id of 0 in this case), we issued

the following Storwize V7000 CLI command:

Using the Storwize V7000 GUI to view the “INTERNAL_POOL” confirms that the Easy Tier™

function

is “Active” and is ready to produce the statistics that will determine how much data should be promoted

to Solid State Drives and how much SSD capacity will be required.



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The following screen shows the Volume mapped to the AIX host system. Notice the “Easy Tier™

Status” for this Volume is currently set to “Measured” with 100GB on HDD and 0GB on SSD.



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The AIX system ran the IORATE workload generation tool for 24 hours which produced a heat data file

reporting the amount of “hot” extents that would benefit if promoted to SSDs.

Using the GUI, the file is located under “Support” and “Show Full log listings” as shown below:



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The IBM Storage Tier Advisor Tool is a Microsoft Windows application that analyzes heat data files

produced by Easy Tier™

and produces a graphical display of the amount of "hot" data per Volume. In

addition it predicts how adding SSD capacity to the measured storage pool could benefit system

performance.

Heat data files are produced approximately once a day when Easy Tier™

is active on one or more storage

pools and updates the activity per Volume since the prior heat data file was produced. This “heat”

information is added to a running tally that will reflect the “heat” activity to-date for the measured pools

and Volumes.

On SAN Volume Controller and Storwize V7000 the heat data file is in the /dumps directory on the

configuration node and is named “dpa_heat.node_name.time_stamp.data”.

Any existing heat data file is overwritten whenever a new heat data file is produced; however, it will

include all the information to date for all measured pools and Volumes. The file must be off-loaded by

the user and processed with the STAT utility and invoked from a Windows command prompt. The user

also has the option of specifying the output directory. The STAT utility creates a set of HTML files and

the user can then open the resulting “index.html” in a browser to view the results.

The SVC / Storwize V7000 Storage Tier Advisor Tool can be downloaded at:

http://www-01.ibm.com/support/docview.wss?uid=ssg1S4000935

Installing the STAT utility places the program files by default in the “Program Files\IBM\STAT”

directory on the local C:\ drive.



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The Storwize V7000 produces a “HEAT” file, which has to be downloaded to the directory that contains

the STAT executable. Right click on the file and a box will display with the option to download and

save the file as shown below:



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Once the “heat” file is in the correct directory run the STAT.exe to generate the STAT HTML reports.

Five HTML reports will be recorded in the “Data Files” directory of the STAT folder under “Program

Files\IBM”, which is the default output location as shown below:



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Following are three of the reports that were obtained running the STAT.exe against the Storwize V7000

“heat” file from our previous testing with an AIX system. The System Summary shows that 20GB of

the AIX Volume had enough I/O operations on specific extents to merit their promotion to SSDs. It also

recommends the SSD configuration and estimated performance improvement.



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Based on the Storage Tier Advisor Tool recommendations, an SSD RAID-5 array/MDisk was added to

the “INTERNAL POOL” using the command line interface (CLI).

(Note: Currently the GUI does not allow the addition of an SSD array/MDisk to an existing HDD pool

using anything other than the SSD Easy Tier preset. In this example we created a RAID-5 array.)

Viewing information about the “INTERNAL_POOL” shows that the SSD backed “mdisk40” has been

added to the pool as shown below:



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Currently the status of the Volume mapped to the AIX system still shows that all 100GB of storage

allocated to this Volume comes from HDDs.

Note: Adding the SSDs to the pool where the AIX Volume was carved from originally was totally

transparent to the host running the IORATE application.



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Depending on where in the Easy Tier™

measurement collection cycle the SSDs were added to the

storage pool it may take several hours before the “hot” extents are migrated to the SSD backed MDisks

in the pool and another heat data file is generated as shown below:

The new “heat” data file was downloaded and placed in the STAT directory.



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The STAT utility was run against this new heat data file and the generated reports will confirm the

20GB of “hot” data was automatically migrated from HDDs to SSDs.



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Using the Storwize V7000 GUI, the status of the Volume mapped to the AIX system shows that 80GB

are located on HDD and 20GB of “hot” extents are located on SSD.



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STATISTICS FROM THE IORATE PROGRAM RUNNING ON AIX

(NO SSDs):

test_number test_name total_sec reads read_resp I/Os_per_sec

1 V7000 Heatmap 90000 20288472 4.43 225

Note: All reads were 8K random read I/Os

STATISTICS FROM THE IORATE PROGRAM RUNNING ON AIX

(USING SSDs):

test_number test_name total_sec reads read_resp I/Os_per_sec

1 V7000 Heatmap 9000 104213061 0.86 1158

Note: All reads were 8K random read I/Os



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Solid State Drives (SSDs) are emerging as an attractive alternative to Hard Disk drives (HDDs) in

today's storage market. With dramatically high throughput, low response times and energy-efficient

characteristics, SSDs have the potential to achieve significant savings in operational costs even though

current acquisition cost per GB is higher than HDDs. To satisfy the majority of workload

characteristics, SSDs need to be used in conjunction with HDDs, and it is critical to choose the right mix

of drives and the right data placement in order to achieve optimal performance at the lowest cost. For

example, maximum value can be derived by placing “hot” data with high I/O density and low response

time requirements on SSDs while targeting HDDs for “cooler” data that is accessed more sequentially

and at lower rates. The Easy Tier™

feature and the IBM Storage Tier Advisor Tool provide insights into

the storage workload and automate the placement of data amongst different storage tiers in order to

achieve optimal performance.

It is important to note that not all workloads will benefit from SSDs. Therefore it is important to start

using the Storage Tier Advisor Tool by activating Easy Tier™

measurement on the pools that one thinks

will benefit from SSD technology and run workloads for several iterations. This will produce evidence

from the STAT utility HTML reports that the customer applications can benefit from the purchase and

installation of SSDs in their IBM Storwize V7000 system.



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The authors of this document would like to express their thanks to the following people for their contributions to make this paper the best possible:

Mark Bruni

Rosemary McCutchen

Craig Gordon

Dominic Pruitt

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