State of solid-state drives
Everyone has a name for it: memory recording, solid-state recording or professional plug-in technology. Whatever it’s called, it’s all flash-memory-based, and as it becomes more ubiquitous in the broadcast industry for onboard recording duties, few are finding much not to like about it. It’s fast, convenient and designed to integrate seamlessly in the digital production chain without analog ingest.
The basis for nearly all solid-state recording, from digital still cameras to HD cameras, is the flash memory chip. Flash is a non-volatile memory chip or chips that can be electrically erased and reprogrammed, and because flash is non-volatile, power is not needed to maintain the data stored in the chip.
The latest transformation of flash memory recording is the solid state drive (SSD). Early SSDs were rack-mounted, power-hungry behemoths. Recently, solid-state drives have been introduced in a PCIe card form factor that plugs into the PCIe bus in a PC, drawing less than 25W. Most recently, several leading manufacturers proposed a new memory card format for the PCIe serial interface to achieve data transfer rates of up to 500Mb/s with potential storage capacities beyond 2TB. The proposed set of specifications hints at higher-performance requirements as camcorders are updated to capture video beyond HD and continuous burst shooting of massive RAW images in DSLRs.
We recently had the opportunity to talk with Travis Cameron, digital media manager at BYU-Hawaii. The BYU-Hawaii Media Lab is an early adopter of new PCIe memory cards. Specifically, BYU-H is using LSI WarpDrive 300GB PCIe SSD cards in its AV operations for a number of demanding scenarios.
BYU-H found the need to record and play multitrack audio using Avid’s Pro Tools in locations where access to the campus fiber-channel connection to the SAN wasn’t available. The computer displayed errors when it couldn’t pull audio from its internal drive fast enough when reading and writing simultaneously. After some research, BYU-H purchased its first WarpDrive 300GB SSD card, with up to 240,000 sustained I/O operations per second and 300GB of solid-state storage capacity. The card solved the Pro Tools issue and was quickly recognized to provide some exciting unexpected solutions. Cameron found that the card also facilitated real-time recording of uncompressed HD and 4K video with a real-time HD-SDI I/O card. The SSD card turns a PC with a HD-SDI I/O card into an uncompressed HD recorder that cruises at SMPTE’s 292M HD-SDI, 1.5Gb/s bit rate. A single 300GB SSD is capable of recording up to three hours of native HD-SDI in real time.
There were no surprises, then, when BYU-H installed their new SSD card. Cameron plugged it in, installed the drivers, formatted the drive and started using it right away. While the most popular SSD card for broadcast and production use only has drivers for PC and Linux, Mac drivers will soon be available. BYU-H moved its page files to the SSD card, which helped everything run faster. The improved read/write speed enabled more tracks on the SSD card than on a SATA drive.
Speed up workflows
Once recorded on the SSD, material can be transferred at high speeds to a SAN RAID system for online editing or storage or an internal SATA drive for nearline editing or storage. Operators accustomed to using FireWire find that SSD transfer times are significantly faster.
Recent independent lab tests revealed that at least one new SSD card is 16 times faster than a six-hard disk array (HDD) and three times faster than a 24-drive array. The same test revealed a SSD response time of .01s, versus .035s for 24-drive array and 0.175s for the six-drive array. SSD power consumption was similarly lower than the HDD arrays.
Typically with speeds an SSD card can deliver, the bottleneck becomes the network itself. BYU-H’s 16Gb bidirectional Fibre-Channel network supports its SSD; 10Gb is a nominal minimum. Operators also learned they could stack two 300GB SSD cards in one computer for 600GB of onboard storage.
MTBF or P/E?
It’s difficult to compare MTBF figures between standard electromechanical hard drives and SSDs. Some hard drive manufacturers claim 1 million hours MTBF, but some broadcast engineers may feel that claim might be a little optimistic. Like hard drives, flash memory and PCIe-based SSD cards can wear out, but for entirely different reasons. Flash memory chips are usually rated in program-erase (P/E) cycles. Some chip firmware or file system drivers increase P/E cycles by counting the writes and remapping blocks, which spreads write operations between sectors using a technique called wear leveling. The latest flash memory chips are rated at anywhere from 100,000 to more than 1 million P/E cycles, but the chip won’t necessarily fail when it has reached its effective life. A chip with a 1 million P/E cycle rating will have approximately 0.02 percent of the sample population turn into a bad block when the write rating is reached for that block.
Writing to flash memory is slower than writing to DRAM, but the speed of reading data from flash memory is quite similar to reading from DRAM. However, flash memory uses much less power and generate less heat than DRAM chips. Some manufacturers of SSDs use an integrated DRAM cache to increase write speeds, and some use algorithms that move data from cache to flash in the background without impacting performance.
BYU-H’s staff and students also found that SSD cards provided a number of significant advantages over recording to local hard drives, one of which was the ability to view and review material in real time at full resolution. Another was the ability to accurately preview green screen setups and recording. Clearly, the length and uncompressed quality of uninterrupted record time is one of its most popular and useful advantages.
As broadcasting moves into the digital age, PCIe-based SSD cards are poised to become a powerful tool for uncompressed HD recording, editing and playback at a relatively modest price.
Editor’s Note: Travis Cameron, digital media manager at the BYU-Hawaii Media Lab, contributed to this article.