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

Transcription

1 Using the Storage Tier Advisor Tool (STAT) and Easy Tier TM on the IBM Storwize V7000 Gonzalo Fuentes Dan Riedel William Wiegand IBM System and Technology Group / IBM Advanced Technical Skills February 3,

2 Introduction 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. 2

3 Test Configuration: 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 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 3

4 Test Methodology 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. 4

5 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. 5

6 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: 6

7 Easy Tier TM Analysis using the STAT Utility 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: Installing the STAT utility places the program files by default in the Program Files\IBM\STAT directory on the local C:\ drive. 7

8 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: 8

9 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: 9

10 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. 10

11 Add SSD Capacity to the Storwize V7000 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: 11

12 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. 12

13 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. 13

14 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. 14

15 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. 15

16 AIX running IORATE Statistics: 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 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 Note: All reads were 8K random read I/Os 16

17 Test Results Graphs: 17

18 Conclusions 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. 18

19 Acknowledgements 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 19