IBM Storwize V7000
|Abstract: SSDs are delivering much more performance in respect to IO/s, comparing to FC or SAS disk drives; but the costs per GB are much higher. SAP systems require both, high performance (IO/s with a low response time) and high capacity. IBM Easy Tier combines the benefits of SSD and HDD, high IO/s and low $/GB, an optimal solution for SAP environments. This Technote describes the necessary setup to use Easy Tier on Storwize V7000|
Solid State Drives (SSDs) are emerging as an attractive alternative to hard disk drives (HDDs) in today's enterprise storage market. With dramatically high throughput, low response times and IO/s energy efficient characteristics, SSDs have the potential to achieve significant savings in operational costs although 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 low cost. For example, maximum value can be derived by placing "hot" data with high IO 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 project aims at developing novel systems and technologies that can develop insights into the storage workload and automate the placement of data amongst different storage tiers in order to achieve the optimal performance through a software, server and storage solution.
Especially SAP systems, including ERP, BW, SCM, SRM, CRM, need high performance in respect to IO/s and high capacity. Here Easy Tier is the best fit to benefits from both worlds.
2) File System setup up
In order to use Easy Tier the SAP data base needs to be installed on a specific file system layout.
This layout is also required to run IBM Tivoli FlashCopy Manager (FCM).
Figure 1: File system layout
As shows in this picture SAP needs to be installed on 3 different Volume Groups:
BIN: To store all executable, binary, and configuration files
DATA: To store the SAP DATA files
LOG: To store the SAP LOG files.
It is not necessary to create a separate VG for "dump".
Obviously the Operating System has its own Volume Group and LUN(s).
This file-system layout matches the requirement of DB2. Nevertheless the basic setup is applicable for Oracle and MS SQL as well: Dedicated volume (-groups) for OS, BIN, DATA and LOG and mirror LOG.
3) Storwize V7000 Sizing
Please have a look at the IBM storage system sizing guideline for SAP environments, and SAPmagic tool
4) Storwize V7000 / SVC setup
By creating a storage pool (managed disk group) with both generic SSD MDisks (classified with the generic_ssd option) and generic HDD MDisks (generic_hdd or default option), Easy Tier is automatically turned on for pools with both SSD MDisks and HDD MDisks. Storwize V7000 does not automatically identify external SSD MDisks; all external MDisks are put into the HDD tier by default. External SSD MDisks must be defined manually. Local (internal) MDisks are automatically classified as generic_ssd or generic_hdd and are placed in the appropriate tier without manual intervention.
4.1) Standard / medium workload
Just the VDisks serving SAP DATA have to be Easy Tier enabled, not LOG; place SAP DATA and SAP LOG into one MDG.
All other data (OS & SAP BIN) should (could) be placed on a HDD-only MDG -- this is in principle non-critical, placing BIN / OS on a separate MDG simplifies manageability of the first MDG in case of FlashCopy usage.
All arrays are RAID 5, 7+1 (MDisks).
Figure 2: Pool / Managed Disk Group definition for medium workload
4.2) High workload
If many, big SAP systems need to be managed, it is recommended to place all (production) logs into one separate Pool / MDG.
LOG writes are a single threaded, sequential workload.
For ever high SAP workload create one RAID 10 array 5+5 to 8+8, and place the single VDisk on the array -- dedicated arrays for LOGs.
Create RAID 5 SSD array(s) (7+1) and place it (them) into the Pool. The number of arrays are just depending on SAP LOG capacity requirements. One VDisks should be place on one array only.
In any case, for SAP LOG ensure a one-to-one relationship between: VDisk 1-1 OS Logical Volume 1-1 File system.
For the DATA Pool use either RAID 5 or RAID 10, the SAPmagic tools provides a recommendation when to use what RAID definition.
Figure 3: Pool / Managed Disk Group definition for high workload
Automatic data placement is enabled by default for storage pools with more than one tier of storage. When automatic data placement is enabled, by default all striped volumes are candidates for automatic data placement. Image mode and sequential volumes are never candidates for automatic data placement. When automatic data placement is enabled, I/O monitoring is done for all volumes whether the volume is a candidate for automatic data placement. Once automatic data placement is enabled, and if there is sufficient activity to warrant relocation, extents will begin to be relocated within a day after enablement. You can control whether Easy Tier automatic data placement and I/O activity monitoring is enabled or disabled by using the settings for each storage pool and each volume. Each command in the following table that can create or change the settings for storage pools can enable or disable Easy Tier functions. Any command that can create or change the settings for volumes can enable or disable automatic data replacement, if automatic data replacement is enabled for the storage pool.
In any case, SSD MDG are configured as RAID 5.
RAID 10 provides just a minimal better performance, but reduces the usable capacity by almost 50%.
Use the max grain size, which is 256 KB
Use an extent size of 1GB (256 MB minimum)
That's all, the SAP system is ready to run on Easy Tier enabled storage.
5) Additional Information
Several other IBM Redbooks and IBM Whitepapers on SDD or Easy Tier are available:
Planning and Design
Enterprise Application Solutions (EAS/ERP); ISV Applications
IBM System p Family; IBM System x Family; IBM System Storage
AIX; Linux; Windows
Storwize V7000, Easy Tier, SSD, SAP, SVC
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