MegaRam 2000: the Ferrari of Storage

The MegaRam 2000, imperial Technology Inc.'s latest solid-state disk storage accelerator, provides exceptional performance and strong fault-tolerance features in a compact form factor to boost database and I/O-intensive applications in enterprise environm

The MegaRam 2000, imperial Technology Inc.s latest solid-state disk storage accelerator, provides exceptional performance and strong fault-tolerance features in a compact form factor to boost database and I/O-intensive applications in enterprise environments.

The MegaRam 2000 SSD (solid-state disk) device is attached to a host server using SCSI or Fibre Channel connections and can be treated like a standard hard drive. The MegaRam SSD uses DRAM (dynamic RAM) to provide data storage. Because the device stores all data in DRAM and lacks mechanical latency, such as head positioning and spinning platters, that occurs during read/write requests in a disk drive, it can deliver a much higher I/O.

However, the significant performance gains come at a cost. Hard disk storage costs less than 5 cents per megabyte, whereas storage on SSD systems can cost well over $10 per megabyte. With such a high price-per-megabyte ratio, SSD is not intended for everyone, and most shops will not be able to justify the cost of implementing such a system.

For sites that can afford them—such as telecommunications companies, financial institutions and some e-businesses—SSD systems are uniquely positioned to provide a specialized way to solve bottleneck problems in high-end database and enterprise applications where other performance-enhancing methods have failed.

Another important point to note when implementing SSD systems is that usually only a small percentage of all the data used in an enterprise application will need to be stored in SSD systems to improve performance. In the case of a database application such as Oracle Corp.s Oracle or Microsoft Corp.s SQL Server, the indices and transaction logs occupy a small portion of the entire database but are most frequently accessed by the application servers during queries and are slowed by the I/O bottlenecks caused by mechanical disks.

The MegaRam 2000 shipped last month at an entry price of $25,000 with 1GB of DRAM. The device we tested included 3GB of DRAM, two Ultra SCSI ports and one Fibre Channel port, a hot-swap uninterruptible power supply, and a single 36GB hard disk for data backup, with a price of $55,750.

Because the Mega- Ram 2000 is a memory-only storage system, data integrity is very important. The MegaRam uses Reed-Solomon EDAC (error detection and correction) circuitry to automatically correct errors up to 6 bytes in size. EDAC error-protection technology is usually found in mainframe systems and is better than the error-correcting code memory used in standard synchronous DRAM, which corrects no more than 1 byte of errors.

The MegaRam 2000 can scale up to 38GB of storage capacity. The entire system has a 2U (3.5-inch) footprint and can be mounted easily on a data center rack.

Iometer metrics

We tested the MegaRams performance using Intel Corp.s Iometer I/O benchmark tool, which measures I/O operations per second. We used a Dell Computer Corp. PowerEdge 2550 with dual 1GHz Pentium III processors as the host server to ensure that we didnt have any CPU bottlenecks. We attached the Mega- Ram to the server using the Fibre Channel port and an Emulex Corp. adapter on the server.

The PowerEdge 2550 has Ultra3 SCSI disk subsystems, and we used a four-disk RAID 5 volume for comparison purposes.

The MegaRam 2000 outperformed the disk array in every test to which we subjected it. In a test scenario using a mixture of random read/write operations common in real-world applications, the MegaRam outperformed the RAID 5 disk array by a large margin. The MegaRam SSD achieved an outstanding throughput of over 5.7MB per second and 2,900 I/Os per second, vs. less than 0.5MB per second and 230 I/Os per second logged by the conventional disk array.

The MegaRam device includes strong fault-tolerance features to ensure that data stored in DRAM is nonvolatile and well protected. In addition to error-correcting DRAM, the system can house two uninterruptible hot-swappable power supplies, redundant fans and a built-in hard drive to back up data.

Installing the MegaRam 2000 proved to be a simple process. It can be mounted to the host using as many as four SCSI or two Fibre Channel interconnects. The embedded SAF (Service Adapter Facility) firmware provides system administration and monitoring, which we accessed via Telnet or terminal emulation. SAF also provides error and event logging, like the memory (correctable and uncorrectable), battery and backup disk error logs. Although the logs are detailed and provide useful information for trouble-shooting, they can be displayed only in the SAF and are not exportable in formats suitable for reporting purposes.

Using SAF, we quickly configured the SSD with a different SCSI ID and logical volumes and also monitored the systems health. The MegaRam 2000 can be configured with multiple partitions called Physical Units with different SCSI IDs and mapped to different SCSI or Fibre Channel ports.

This feature allows the MegaRam to be shared among different hosts, providing a performance boost to multiple systems. The memory may be partitioned to form up to 16 PUs, and each PU ranges from 128KB to the maximum storage capacity. In our tests, we used the default configuration using one SCSI ID and a single PU.

We were disappointed that no Web browser-based management is available. It would be nice to be able to remotely monitor and manage the MegaRam 2000 with a Web browser. A future release of the MegaRam will use SNMP to support management software such as Hewlett-Packard Co.s OpenView management suite, which will ease the task of managing multiple SSD devices.

MegaRam 2000 buyers should be able to upgrade to the new SNMP features when they become available by upgrading the firmware.