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Introduction 3 Tier Architecture – – – Workload Generator Application Server Database Server Workload Generator Tier 42 x Compaq DL360 – 512 MB RAM – 2 CPU (Pentium III 1 GHz) – Running Mercury Loadrunner to simulate Applications users – Rack-mounted in a single cabinet Application Server Tier 12 x Compaq ES40 – – – – – 16 GB RAM 3 CPU (833 MHz) Tru64 5.1 Local Storage (no Fibre Channel) No Memory Channel Cards As there is no shared resource in the Application Servers we can expect linear scalability Database Server Tier 4 x Compaq ES40 – 16 GB RAM – 3 CPU (833 MHz) – Tru64 5.1 Patchkit 4 – Dual Fibre Channel Cards – Dual Memory Channel Interconnects – Tru64 Clustered Filesystem used for OS + Oracle Binaries + Datafiles Overall Picture DL360 DL360 OLTP DL360 ……………... OLTP OLTP DL360 DL360 Concurrent Processing 9i Real Application Clusters • Scalability • Availability • Reduce Total Cost of Ownership - Hardware Procurement Costs - Database Server Consolidation Traditional Shared-Disk Clustered Databases Maintaining data coherency is a hard problem – – Need to synchronize updates to shared data The disk is the only medium for data sharing Disk I/O latencies appear in the critical path when multiple nodes access shared data Disk-based coherency is the main bottleneck to achieving a scalable shared disk cluster – Only synthetic fully partitioned workloads scale! Disk Based Coherency – Parallel Server 2. Update Block A DLM DLM Shared Memory/Global Area shared SQL 3. Request access to Block A Shared Memory/Global Area log buffer shared SQL log buffer . .. . .. ... Ping 1. Read Block A 4. Block A 5. Access Block A Block A Shared Disk Database • To Fix: Go to Interconnect based coherency Oracle Real Application Clusters (RAC) An application transparent clustered database – single node applications run and scale with no changes – To Application logic – Or to Oracle database structures Cluster interconnect fabric replaces the disk as the medium for inter-node data sharing Cache Fusion protocol for data sharing results in a scalable cluster for multiple differing workload types A 9i RAC Database Network Users Low Latency Interconnect High Speed Switch or Interconnect Clustered Database Servers Hub or Switch Fabric Mirrored Disk Subsystem Storage Area Network Oracle9i Real Application Clusters Base Technology (patented) : DB Cache Fusion ´Fused´ DB cache SGA Shared Pool SGA Buffer Cache Buffer Cache DB cache1 DB cache2 Inter-connect All DB cache operations reference 1. the local DB cache 2. all remote DB caches SGA Shared Pool Oracle9i Real Application Clusters Base Technology (patented) : DB Cache Fusion ´Fused´ DB cache SGA SGA Shared Pool Buffer Cache DB cache1 Shared Pool DB cache2 Inter-connect All DB cache operations reference 1. the local DB cache 2. all remote DB caches SGA What is Cache Fusion? The underlying technology that enables RAC Protocol that allows instances to combine their data caches into a shared global cache – Global Cache Service (GCS) coordinates sharing Key features are – Direct sharing of volatile buffer caches – Efficient inter-node messaging framework – Fast recovery from node failures using cache and CPU resources from all surviving node Benchmarks and Customer implementations show 1.85 to 1.9 * scalability with the addition of each node Data Sharing Problem Read Sharing for Queries – query needs to read a data block that is currently in another instance’s buffer cache. Write Sharing for Updates – update needs to modify a data block that is currently in another instance’s buffer cache. With Cache Fusion, a disk read is performed only if the block is not already in the global shared cache Cache Fusion Read Sharing Uses Oracle’s Consistent Read (CR) scheme – – undo is applied to make a block transactionally consistent to a System Change Number (SCN). a CR copy is shipped to the requesting instance 1 Query SCN 200 225 Data Block 200 CR Copy 2 3 Instance A Instance B Cache Fusion Write Sharing Multiple dirty copies of a data block can exist in the global cache, but only one is current The current copy can move between instances without first being written to disk – Changes are logged if not already on disk Non-current dirty copies can directly service queries from any node and instance recovery Cache Fusion Write Sharing Instance A Instance B 4 Current 225 Update Block 10 1 Master 2 3 Copy 225 Requester GCS 200 Instance C Holder Recovery in a RAC Database Survival of one instance guarantees data availability Recovery cost is proportional to the number of failures, not the total number of RAC nodes – – cached copies in surviving nodes are used only redo logs from failed instances are applied Eliminates disk reads for blocks that are present in a surviving instance’s buffer cache. Global cache is available after an initial log scan, well before redo application begins. Database Server Consolidation with 9iRAC Mixed Apps and Database Environment App1 App2 App3 Phase 1 Mixed Apps with common Database but separate data models Mixed Apps with common Database but ‘single version of the truth’ App1 App2 App3 App1 App2 App3 Real Application Cluster Real Application Cluster Phase 2 Phase 3 • 9iRAC will support mixed workloads (OLTP/DSS) within common DB Comparison of Common Interconnects Name Latency Protocol Memory Channel .003 milliseconds RDG Fast Ethernet A few milliseconds UDP Gigabit Ethernet A few milliseconds UDP RDG = Reliable Datagram UDP = User Datagram Protocol Throughput 100MB/s 10MB/s 100MB/s Comparison of Common Interconnects Name Latency Protocol Throughput HP Hyper Fabric 2 .022 milliseconds HMP 400MB/s HMP = Hyper Messaging Protocol Failover - 1 Server 1 Instance 1 Server 2 Instance 2 • NB. This is not what you would do in production! Server 3 Instance 3 Shared Database Server 4 Instance 4 Failover - 1 Concurrent Manager - Batch Server 1 Instance 1 2027 OLTP Users Server 2 Instance 2 2027 OLTP Users Server 3 Instance 3 • No headroom within cluster to fail over any users in the event of an unplanned outage Shared Database 2027 OLTP Users Server 4 Instance 4 Failover - 1 Concurrent Manager - Batch Server 1 Instance 1 2027 OLTP Users Server 2 Instance 2 • Uncontrolled shutdown of Instance 4 2027 OLTP Users Server 3 Instance 3 Shared Database 2027 OLTP Users Server 4 Instance 4 Failover - 1 Concurrent Manager - Batch Server 1 Instance 1 2027 OLTP Users Server 2 Instance 2 • Surviving Instance (1,2 or 3) performs instance recovery 2027 OLTP Users Server 3 Instance 3 Shared Database Server 4 Instance 4 Failover - 2 (Mixed Workload) Server 1 Instance 1 Server 2 Instance 2 • NB. This is what you could do in production! Server 3 Instance 3 Shared Database Server 4 Instance 4 Failover - 2 (Mixed Workload) Concurrent Manager - Batch Server 1 Instance 1 OLTP Workload Server 2 Instance 2 Free Instance Server 3 Instance 3 • Headroom exists within cluster to fail over any users in the event of an unplanned outage Shared Database DataWarehouse Workload Server 4 Instance 4 Failover - 2 (Mixed Workload) Concurrent Manager - Batch Server 1 Instance 1 OLTP Workload Server 2 Instance 2 DataWarehouse Workload Server 3 Instance 3 • Uncontrolled shutdown of Instance 4 • DW Workload fails over to free Instance 3 Shared Database Server 4 Instance 4 Transparent Application Failover (TAF) (Recovery with Hot Failover) • Login context maintained • Little or no user downtime Shared Memory/Global Area shared SQL log buffer Shared Memory/Global Area shared SQL log buffer Shared Memory/Global Area . . .. . . Shared Disk Database shared SQL log buffer Shared Memory/Global Area shared SQL log buffer Transparent Application Failover (TAF) Mission Critical Availability TAF Protects or fails-over: • applications using OCI8 (ODBC, JDBC (thick), Oracle objects for OLE, SQL*PLUS) • client-server connections • user session state • active cursors (select statements) TAF can also be used to gracefully shutdown a system