Technology
Today there is a growing market for digital media storage solutions, fueled by the availability of powerful, easy to use media center computer hardware and software applications. Digital media includes:
- Digital photos: originals, edits, albums and slide shows.
- Digital videos: home movies, performances, graduations, training etc.
- Digital music: recordings, downloaded music and ripped CD’s.
- Recorded television broadcasts: both high definition and standard definition.
A common thread between all these applications is the need for reliable mass data storage. Not only are digital media files becoming larger and larger, but, after spending hundreds of hours capturing, copying and organizing digital media, users should not have to risk losing their time (and possibly their data if the original becomes unavailable) due to device failure.
The traditional approach to providing protection against failing hard drive devices is through the use of RAID[1] technology. But RAID technology was invented in an era of slow, low capacity hard drives (circa 1987). The primary motivation for organizing hard drives into arrays was to be able to stripe data across them in order to increase the storage system bandwidth and capacity, while also maintaining or increasing it’s reliability. The bandwidth of multiple hard drives operating in parallel was necessary to implement many applications, for example, video capture and display.
Today, hard drive speed and capacity are well matched to almost all digital media applications. Of course, a storage system can never be too fast or too large, but today’s technology is more than sufficient for most users. As long as the storage system provides a certain minimum level of performance, other factors become much more important:
- Ease of installation
- Easy capacity expansion.
- Ease of integration with other systems.
- Easy recovery from disk device failure.
- Immunity from catastrophic full data loss.
- Good multiple-stream read performance.
- Adequate write performance.
Lime Technology believes that there is a market for a new wrinkle on the old RAID technology. Our approach uses a storage organization we call unRAID™. unRAID™ is similar to RAID-4 in that for every n hard drives, there are n-1 data drives, and a single fixed parity drive. This provides similar drive failure protection as other RAID organizations:
- Tolerates a single failed hard drive. Array parity permits reconstruction of a single failed data disk.
- Tolerates single drive read errors . Read errors from a single disk are corrected "on-the-fly".
Unlike other RAID organizations, however, files are not striped across the data drives. Instead, each data drive is formatted normally with its own file system. The unRAID™ organization offers several key advantages over other RAID systems:
- Increased flexibility: not all hard drives need to be the same size or speed. The only requirement is that the parity drive must be as large as or larger than any of the data drives.
- Easier expansion: new data drives may be added to the array without disturbing the data on the other drives. Since data is not striped, no lengthy stripe reorganization needs to take place before the new storage is available.
- Better fault tolerance: in the unlikely event of catastrophic hardware or software failure, data corruption would be much more isolated than that which could occur with other RAID organizations. It is almost impossible to lose all your data, since each individual data drive has its own file system.
- Better power management: not all hard drives are required to be spinning in order to access data normally; hard drives not in use may be spun down.
- Potentially better multiple-stream read performance. If multiple files are read from different disks, overall read performance can be higher than with other RAID organizations.
All Lime Technology server products are based on unRAID™ technology. We believe our products offer superior features and value in the digital media storage market.
- Footnotes:
- [1] mirroring is considered a type of RAID, specifically RAID-1.
