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"Solid" Performance from Solid State StorageBy Drew RobbMarch 10, 2005
Magnetic disks must be written to or read from by a physical arm traveling across the disk. This mechanical fact significantly constrains performance. According to most studies, the fastest hard disk drives have access times equal to 5 milliseconds (peak performance). Multiply this by the billions of operations demanded by users daily, and a considerable lag results. Solid state disks (SSD) solve the problem by replacing spinning disk drives with memory chips (typically DDRRAM) to read and write data. Access times come down to as little as 20 microseconds (250 times faster than hard disk drives). The downside, of course, is that SDRAM-based disks require power to maintain their data. A power loss means you have lost your data. This is remedied by including backup batteries and backup hard disk drives so that any data written to the SDRAM can be backed up or mirrored to these drives. You won't see SSD on laptops or desktops, though. The few workstations that do incorporate solid state are used for extremely high-end purposes where the price/performance ratio makes sense. According to Woody Hutsell, Executive Vice President of leading SSD maker Texas Memory Systems (TMS) of Houston, Texas, its RamSan-320 SSD product costs between $36,000 and $108,000 for 16 to 64 GB. Expensive, yes. But the whole point is not just holding data, but moving data. Where administrators have to stripe performance across numerous hard disks or RAID units, for example, solid state disk becomes an attractive alternative. After all, a single 3U appliance can do the raw I/O work of hundreds of conventional disk drives. And that can make a big difference in the storage world. Batch processes that used to take a full day have shrunk down to 20 minutes when SSD is incorporated. ERP Performance Gain Chatsworth Products Inc. (CPI) supplies racks, cable management systems, and related materials to the IT industry. CPI has an Enterprise Resource Planning (ERP) database (SQL 7.0) on redundant Dell PowerEdge servers and Dell 51F Fibre Channel switches. Highly concentrated access to the enterprise resource planning (ERP) system during short periods of time caused slow queries, database deadlocks, and SQL lockups. This resulted in frustrated end-users and database integrity issues as multiple users experienced deadlocks. Wait times for frequently run queries were around half a minute. CPI's IT staff had tuned the database code and implemented infrastructural changes to markedly improve performance, but hit a performance wall when it came to storage. The organization connected the TMS RamSan-320 solid state disk to a Dell-based Storage Areas Network (SAN). This consisted of Dell servers, switches, and SAN management software. The most frequently accessed tables from the database were placed on the RamSan solid state disk. In addition, application temp space was also routed to the RamSan. The Result: 700% faster queries and improved stability "One of our frequently run SQL queries returns all manufacturing orders for a given location and work center," said Jerry Guy, Sr. Database Administrator at CPI. "Prior to installing the RamSan, that query typically took 25 seconds. That same query now runs in three to four seconds. This has drastically cut down on trouble calls due to database deadlocks and the problems they can cause with database integrity." Military Secret Texas Memory Systems began life designing systems to meet the needs of the U.S. defense industry, which remains one of its primary customers. This market has always demanded top performance. What the RanSAN product line represents is a leaking of these military secrets into the commercial sector. Although it is only really viable in very high performance environments, it's hard to argue with the overall price performance numbers. The RamSan-320, for instance, scored well on benchmark testing by the Storage Performance Council. It achieved an SPC-1 I/O per second rate of 112,491.34 and Price-Performance value of $1.50 at a capacity of 68.719 GB. This makes the medium the most economical high performance storage available. That said, if you do not have applications that demand high performance, or are not significantly impacted by the bottlenecks of conventional hard disk based storage, you do not stand to benefit. But there are applications in the storage field where the performance boost far outweighs the cost.
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