Exadata Storage Servers

Exadata Extreme Flash (EF) Storage Server is the foundation of a database-optimized all-flash Exadata Database Machine. Each EF Storage Server contains four capacity-optimized 30.72 TB flash drives for an aggregate raw storage capacity of 122.88 TB,  increasing the usable storage capacity by 2.4x (1).

Each EF Storage Server includes four 6.8 TB performance-optimized flash drives, offering 27.2 TB of Exadata Smart Flash Cache. The Smart Flash Cache increases in size by 11.5x (2) and is used to satisfy read and write requests. Exadata delivers ultra-high performance by placing all the flash devices directly on the high-speed PCIe interface rather than behind slow disk controllers. Exadata EF Storage Servers include up to 1.25 TB of DDR5 Exadata RDMA Memory (XRMEM) as a data acceleration tier in front of flash cache.

For data warehouse environments that require the highest performance, Exadata X11M HC and EF storage servers are both capable of scanning data in flash at up to 100 GB/s with Smart Scan and up to 8.5 TB/s by reading columnar data cached in Exadata RDMA Memory (3) from a single rack configuration.

These represent real-world, end-to-end performance metrics measured while running SQL workloads with standard 8K database I/O sizes inside a single rack Exadata system. Exadata's performance on real Oracle Database workloads is orders of magnitude faster than traditional storage array architectures and much faster than current all-flash storage arrays.

(1) Compared to X9M Extreme Flash Storage Servers

(2) Exadata X7 – X9M Extreme Flash Storage Servers allocated 2.32 TB to Smart Flash Cache of the total 51.2 TB raw flash capacity per server

(3) Elastic configuration with 2x Exadata X11M Database Servers and 17x Exadata X11M High Capacity or 17x Exadata X11M Extreme Flash Storage Servers

Each HC Storage Server includes twelve 22 TB disk drives with 264 TB total raw disk capacity. It also has four 6.8 TB performance-optimized flash drives for a total raw capacity of 27.2 TB of Exadata Smart Flash Cache and up to 1.25 TB of Exadata RDMA Memory (XRMEM) in front of flash to boost performance further.

Flash in the HC Storage Server can be used directly as flash disks but is almost always configured as a flash cache (Exadata Smart Flash Cache) in front of disk storage and behind the Exadata RDMA Memory. Exadata Smart Flash Cache is used with the XRMEM Data Accelerator to automatically cache frequently accessed data while keeping infrequently accessed data on disk, delivering the high I/O rates and fast response times of flash with the large capacity and low cost of disk. Exadata uniquely understands database workloads and knows when to avoid caching data that negatively affects overall performance. For example, if large write I/Os caused by backups or large table scans are likely to disrupt higher-priority OLTP or scan operations, those large I/Os will bypass the flash cache and go straight to disk. Otherwise, Exadata System Software will utilize additional spare flash capacity and I/O bandwidth to optimize performance by caching these I/Os. Administrators can also manually provide SQL directives to ensure that specific tables, indexes, or partitions are preferentially retained in the flash cache.

It is common for hit rates in the Exadata Smart Flash Cache to be over 95%, or even 99% in real-world database workloads, yielding an effective flash capacity many times larger than the physical flash.

Exadata Smart Flash Cache also caches database block writes using Exadata Write-Back Flash Cache technology. Write caching eliminates disk bottlenecks in large-scale OLTP and batch workloads. The flash write capacity of a single Exadata Database Machine X11M rack reaches 13 million 8K flash write I/O operations per second (IOPS) (1). The Exadata Write-Back Flash Cache is transparent, persistent, and fully redundant, with performance comparable to dozens of enterprise disk arrays with thousands of disk drives.

The automatic data tiering between memory, flash, and disk in Exadata provides tremendous advantages over other flash-based solutions. Many storage vendors have developed flash-only arrays to achieve higher performance than traditional disk-based arrays. However, they cannot match the cost advantages of Exadata’s smart data tiering between disk and flash. Traditional flash arrays lack Exadata’s unique database-aware storage optimization. In addition, generic data deduplication provided by some flash arrays may be effective for workloads such as Virtual Desktop Infrastructure environments, but not for databases. In addition to utilizing its integrated and optimized hardware architecture, Exadata delivers superior performance by offloading data-intensive processing to unique algorithms in storage which have been specifically optimized for Oracle Database.

(1) Elastic configuration with 6x Exadata X11M Database Servers and 13x Exadata X11M Extreme Flash Storage Servers or 13x Exadata X11M High Capacity Storage Servers

As an entry point into the Exadata ecosystem, or for smaller workloads, Exadata High Capacity-Z Storage Servers contain less memory, flash, and hard drive capacity than the High Capacity Storage Server.

This storage option extends Exadata’s operational and management benefits to less frequently accessed data that must be kept online. Leveraging the same scale-out architecture as the HC and EF storage servers, XT storage delivers the efficiency, performance, and innovation you expect from Exadata while providing cost-effective additional storage capacity.

XT storage provides cost-effective, scalable storage for data that is accessed less often but must stay online for retention or compliance, as well as for databases with lower performance needs. XT is engineered to be shared among multiple database clusters, can quickly and easily expand storage capacity for all your databases, and supports both Exascale and ASM.

Combining Extreme Flash, High Capacity, and Extended Storage within an Exadata configuration allows customers to define a true Information Lifecycle Management policy. As data ages, it can be moved between the three storage tiers to ensure data is on the appropriate storage tier for its usage and retention requirements. Coupled with Automatic Data Optimization, part of Oracle Advanced Compression, customers can define policies to automate this movement between storage tiers and compression levels.