I/O Priority Manager & WLM

Transcription

1 ELADIO FAIGAL Consulting IT Specialist Storage Solutions May Coppell, Texas efaigal@us.ibm.com I/O Priority Manager & WLM a presentation for the DFW zsystems Users group

2 Having the right infrastructure is essential: IBM DS8000 is ranked #1 storage for the Mainframe Market share 4Q 2016 HP EMC Hitachi Global market acceptance #1 with 48% market share Clear leadership position 90% greater revenue than next closest competitor IBM 0% 25% 50% 19 of the top 20 world largest banks use DS8000 for core banking data Source: Calculations based on data from IDC Worldwide Quarterly Disk Storage Systems Tracker, 2016Q4 (Worldwide vendor revenue for external storage attached to z/os hosts)

3 Industry Trends Customers purchasing larger disk subsystems due to Server consolidation Logical partitions Virtual machines Cost incentives Varying drive sizes Automated tiering software Ease of management with fewer physical islands Less staff In some cases, less experience May create workload contention One misbehaving application can create a domino effect The application driving a very high I/O workload may not be the critical workload and may in fact be harming other application service times Need to protect important I/Os from less important I/Os 3

4 DS8000 I/O Priority Manager Application level Quality of Service (QoS) DS8000 IOPM provides a mechanism to manage quality of service for I/O operations associated with critical workloads and to give them priority over other I/O operations associated with non-critical workloads Adaptive based on workload and contention for resources in the storage subsystem 4

5 Introducing the DS8000 I/O Priority Manager DS8000 I/O Priority Manager (IOPM) Capacity based DS8000 LIC feature ( I/O Priority Manager ) for active I/O management Capacity ordered for scope FB CKD All There are monitoring capabilities (more on that later) that do not require the license feature Objective is to protect high importance workload from poor response times caused by low importance workload saturating the disk resources 5

6 Overview of DS8000 I/O Priority Manager Disks and ranks of disk have a certain capability to support I/O This is based on: Geometry of disks RAID protection scheme in use Size (width) of the array Type of disk (Solid State Drive, Enterprise, Nearline) DS8000 calculates a value based on these parameters These form the optimum response time DS8000 monitors the disk resources to determine if a resource is becoming saturated At this time, the DS8000 monitors only disk ranks 6

7 How DS8000 I/O Priority Manager Works I/O Priority Manager monitors rank response times Keeps history of response time by rank When resources become saturated, IOPM will delay lower priority I/Os to allow higher priority I/Os to complete faster Storage Administrator places volumes into four categories Low priority Medium priority High priority Default (no category assigned) 7

8 Quality of Service Recall that optimal response time of a rank is estimated by the DS8000 based on Geometry of disks (146 GB/15K 900 GB/10K, 3 TB/7.2K) RAID protection scheme in use (RAID 5/6/10) Size (width) of the array (3x3, 4x4, 6+P, 7+P) Type of disk (Solid State Drive, Enterprise, Nearline) IOPM uses this optimal response time to calculate a QoS value A QoS value of 100 indicates that I/Os are receiving optimal response times A QoS value of 50 indicates that I/Os are seeing response times that are twice as long as optimum But it can go over a value of 100 when exceeding objectives 8

9 Quality of Service - continued Example: If optimal response time is 5 ms And the average response time is 8 ms Then the QoS calculated value is or 62.5 Typically QoS ranges between 0 and 100 Values near 100 means that the I/Os are currently experiencing near optimal response times A value of 50 means that I/Os are currently experiencing response times that are approximately twice as long as their optimal response time But a value higher than 100 is possible when response times are exceeding their optimal response times 9

10 Supported Environments DS8880, DS8870, DS8800 and DS8700 only R6.1 LMC introduced support for FB volumes R6.2 LMC introduced support for CKD volumes z/vm, z/vse and older levels of z/os support CKD volumes but at the volume level Additional z/os enhanced support (synergy) introduced with APAR OA32298 and z/os V1.11 This APAR introduces support for I/O level prioritization More on this later DS8000 must have 242x-941 or 242x-951 or 242x-961 FC #0784 (I/O Priority Manager) 239x-LFA FC # (I/O Priority Manager/TB authorization) 10

11 DS8000 I/O Priority Manager and FB Volumes Granularity is at the volume or lun level Can set FB lun to a specific performance policy If not otherwise specified, system will use default performance policy If upgraded from old levels of microcode, all luns inherit the default performance policy Default performance policy means don t speed up and don t slow down 11

12 Performance Policies for Open Systems Low performance policy Volumes assigned to this performance policy have no QoS target No goal for response times Medium performance policy Volumes assigned to this performance policy have a QoS target of 40 Attempt to stay under 2.5 times the optimal response time of the rank High performance policy Volumes assigned to this performance policy have a QoS target of 70 Attempt to stay under 1.5 times the optimal response time of the rank Default performance policy No QoS target Volumes never delayed by I/O Priority Manager Existing volumes on DS8000 that is upgraded to LMC R6.1+ level of microcode inherit this performance policy Storage Administrator can/should set the performance policy of these after upgrade if using IOPM 12

13 Performance Groups for FB Volumes Performance Groups are used to assign a numerical value to a performance policy 16 Performance Groups (0 through 15) PG1 PG5: Used for volumes requiring higher performance PG6 PG10: Used for volumes with medium performance requirements PG11-PG15: Used for volumes with no performance requirements PG0: Used for default performance policy 13

14 FB Performance Group Mapping Performance Group Performance Policy Priority (CLI or GUI) QoS Target Default Name Fixed Block High Priority Fixed Block High Priority Fixed Block High Priority Fixed Block High Priority Fixed Block High Priority Fixed Block Medium Priority Fixed Block Medium Priority Fixed Block Medium Priority Fixed Block Medium Priority Fixed Block Medium Priority Fixed Block Low Priority Fixed Block Low Priority Fixed Block Low Priority Fixed Block Low Priority Fixed Block Low Priority 14

15 Mode of Operation I/O Priority Manager has three modes of operation Disabled Monitor Manage Disabled mode does not monitor nor manage any resources and will not alter I/O response times Monitor mode will monitor the rank utilization and will keep statistics that are available in the performance data. No I/O response times are delayed Monitor mode can optionally send SNMP traps Statistics can be reported with either the DS Storage Manager or using DSCLI interface No feature license is required to support Monitor mode Continued 15

16 Mode of Operation - continued Managed mode will monitor the resources, keep statistics and will be able to alter response times by delaying I/Os that are in the low and medium performance groups Managed mode can optionally send SNMP traps I/O response times to volumes that are classified as low and medium performance groups can be delayed Statistics can be reported with either the DS Storage Manager or using DSCLI interface The I/O Priority Manager feature license is required to support Managed mode 16

17 IOPM - Operation When monitoring or management is enabled Behavior of rank stage/destage operations is monitored to detect when rank is running at saturation ( Very High Usage ) If SNMPs are enabled, Up to 16 SNMP traps in 24 hour window SNMP traps issued when entering saturation or every 8 hours if in saturation mode Rank enters saturation state if in saturation for 5 consecutive 1 minute samples Rank exits saturation state if not in saturation for 3 of 5 consecutive 1 min. samples SNMP alert is a trigger to look at performance statistics, if analysis is desired 17

18 IOPM Operation - continued When management is enabled I/O operations in a performance group that is managed and that are associated with a rank that is not close to saturation are not delayed I/O operations in a performance group that is managed and that are associated with a rank that is close to saturation ( High Usage ) may be delayed based the performance policy I/O with Low Priority performance policy is impacted as needed to improve QoS of Standard and High Priority I/O I/O with Medium Priority performance policy is impacted less than Low Priority, and only if needed to improve the QoS of High Priority I/O with High Priority performance policy is not impacted Default performance group is never delayed 18

19 DS8000 I/O Priority Manager Statistics Each Performance Group has statistics for a set of volumes Multiple performance groups per performance policy to manage different sets of volumes Performance statistics samples are generated every 60 seconds. The DS8000 maintains statistics for last 60 1-minute intervals 60 5-minute intervals minute intervals 60 1-hour intervals 60 4-hour intervals 60 1-day intervals Statistics can be offloaded DS/CLI or DS/GUI query Resource report Performance group report Offload request can specify a period of time and the sample interval User may iterate setting volume performance groups and analyzing statistics to tune the result. 19

20 I/O Priority Manager and CKD Volumes Without z/os software support On ranks with contention, I/O to a volume is managed according to the performance group of the volume Volumes are assigned to a policy (similar to FB volumes) With z/os software support User assign application priorities via Workload Manager (WLM) z/os assigns an importance value to each I/O based on WLM inputs z/os assigns an achievement value to each I/O based on prior history of I/O response times for I/O with same importance and based on WLM expectations for response time Importance and achievement value on I/O associates this I/O with a performance policy On ranks in contention, I/O is managed according to I/O s performance policy 20

21 WLM and Service Classes A service class is a group of work which has the same performance goals, resource requirements or business importance For workload management, you assign a service goal Three types of Goals (response time goals, execution velocity and discretionary) Examples: 80% complete within 00:00: Average response time Execution velocity of 60 Discretionary 21

22 Sample Service Class 22

23 WLM Activation for IOPM 23

24 WLM Support for I/O Priority Manager in DS8000 Goal Achievement Data WLM derives goal achievement data for service class periods as follows Response Time goal: Importance of period Goal Achievement Value is derived from Performance Index (PI) Dynamic management considering goal achievement of service class Velocity goal: Importance of period Velocity level Static management considering specified goal of service class System service classes Importance: 0 Goal Achievement Value: 0 (no monitor) No management Discretionary goal: Importance: 6 Goal Achievement Value: 1 Static management considering goal type I/O Priority Manager assigns I/O request a Performance Class corresponding to the passed Goal Achievement Data Each Performance Class is associated with a certain maximum throttling level Importance = 2, PI = 1.9 Performance Index Goal Achievement Value PI <= (significantly overachieve) 0.5 < PI <= (overachieve) 0.7 < PI <= (slightly over achieve) 0.9 < PI < (achieve) 1.4 <= PI < (slightly under achieve) 2.5 <= PI < (under achieve) PI >= (significantly under achieve) WLM I/O Priority Manager Performance Class = 3 24

25 SYS1.PARMLIB Updates Member IEAOPTxx has a new statement option STORAGESERVERMGT STORAGESERVERMGT=NO disables I/O Priority Manager and IOS does not assign values to the I/O request representing Importance or Achievement values STORAGESERVERMGT=YES enables I/O Priority Manager IOS assigns Importance and Achievement values to the I/O DS8000 prioritizes I/O based on those values When STORAGESERVERMGMT=YES Service class periods with response time goal the goal achievement and importance are considered Service class periods with a velocity goal the velocity goal and importance are considered For service class periods with a discretionary goal can be throttled if needed I/O requests associated with system-provided service classes SYSTEM, SYSSTC, SYSSTC1-SYSSTC5 are not managed by the I/O Priority Manager 25

26 Performance Groups and Policies CKD performance groups and performance policy mapping CKD performance groups are 0, Performance groups not used, but mapped to performance policy 0 CKD performance policies Performance policy # = performance group # (e.g. PP19->PG19) 0 = no management no delay added, no QOS target = high priority = medium priority = low priority

27 Performance Groups and Policies Recall that FB performance groups are 0-15 Note: CKD and FB volumes are not placed on same ranks but may share same device adapters I/O with low priority is delayed up to maximum allowed before delaying I/O with medium priority Delay only added if on rank with contention Delay added only if there is I/O with higher priority that is not meeting QOS target Delay is decreased if all higher priority I/Os are exceeding their QOS Delays to lower priority workloads do not exceed 200 ms 27

28 CKD Performance Group Mapping 28 Performance Group Performance Policy Priority (CLI or GUI) QoS Target Default Name No Management No Management No Management CKD High Priority CKD High Priority CKD High Priority CKD Medium Priority CKD Medium Priority CKD Medium Priority CKD Medium Priority CKD Low Priority CKD Low Priority CKD Low Priority CKD Low Priority CKD Low Priority CKD Low Priority 6

29 DS8000 I/O Priority Manager Example With I/O Performance Manager, the critical (favored) workloads are protected from other non-critical (non-favored) workloads sharing the same resources. DB like workload DB like workload Favored Non-favored Favored Non-favored Throughput (IO/s) Response Time (ms) Time (min) Time (min) 29

30 I/O Priority Manager and Easy Tier I/O Priority Manager attempts to make sure that the most important I/Os get serviced Will throttle lower priority workload, if necessary, to meet the service objectives Does not promote/demote any extents Does not look at the rank utilization with an eye to rebalancing resources Easy Tier in auto mode attempts to relocate extents to the storage tier that is appropriate for the frequency of host access Promotes hot extents to ranks of a higher class and will demote cold extents to ranks of a lower class (north/south) Relocate extents between similar ranks within a tier to distribute workload evenly to avoid overloading (east/west) 30

31 QoS - I/O Priority Manager and Work Load Manager DS8880 Application A and B initiate an I/O operation to the same DS8880 rank (may be different logical volumes) zwlm sets the I/O importance value according to the application priority as defined by system administrator If resources are constrained within the DS8880 (very high utilization on the disk rank), I/O Priority Manager will handle the highest priority I/O request first and may throttle low priority I/Os to guarantee a certain service level

32 Additional Sources for Information IBM DS8000 I/O Priority Manager Redpaper (REDP-4760) z/os new function support APAR OA IBM System z DS8000 I/O Priority Manager Whitepaper 32

33 Questions 33