6/18/2010 6:00 AM
In the first part of this series, we examined the basic technology underlying LTO backup/archive systems. We also looked at some key cost comparisons between using disk and tape as archive platforms. Now it’s time to examine other issues surrounding backup and archive storage.
More on LTO technology
In the last article, we focused on LTO-5 technology. Even so, there are plenty of similar solutions available in LTO-3 and LTO-4 configurations. Two key differences between the systems are speed and capacity.
An LTO-3 drive runs at 80MB/s. An LTO-4 drive has a maximum data transfer speed of 120MB/s. The LTO-5 standard specifies a maximum transfer speed of 140MB/s.
An LTO-3 cassette can hold 400GB of data. An LTO-4 cassette holds twice as much data, 800GB. In addition to the double storage capacity, LTO-4 decks provide drive-level data encryption. Encryption takes place within the drive and at line speed.
The LTO-5 standard doubles the available storage capacity to 1.5TB, but increases the drive’s speed only by 10 percent. The reasoning behind not doubling the drive speed seems to be that manufacturer’s need to focus on higher capacity, not higher throughput. By maintaining the lower speed, the platform helps maintain reliable data read/write characteristics while focusing on more storage per cassette.
Another advantage of LTO-5 is that it supports media partitioning via an IBM technology called Linear Tape File System (LTFS). This feature permits the drive to two variable-length partitions on the tape. Each part ion can be used for backup and other applications added by third parties. Through LTFS, the drive can write an index at the head of the tape followed by data. This permits faster data access. And even more importantly, writing an index in LTFS format at the head of the tape means each cartridge is self describing. The tape can be read by any reader, even one not running backup software.
The LTO-5 platform is targeted at archiving applications. In fact, it is highly targeted at broadcast and content producer applications. Because HD, digital cinema and 3-D applications require huge amounts of data, LTO-5 becomes a good fit in these applications. Not insignificant, an LTO-5 tape can be as little as 5 percent as costly as a D5 tape, plus you get the advantage of automation. Clearly, LTO tape-based solutions will continue to advance in these media applications.
An industry association called Active Archive Alliance has been formed to support the development of more tape-based archive broadcast and production-oriented solutions. The addition of LTFS is a good fit for such applications.
Backup isn’t archive
Many engineers use the terms backup and archive interchangeably. They are distinctly different functions. A backup system stores content (data) that may be regularly needed for production. An archive contains content that a facility does not expect to need on a continuing basis. As an example, the news department doesn’t need immediate 24/7 access to last year’s Dec. 22 newscast. It can, however, get that material from the archive when necessary. It just may take some time.
According to the Storage Networking Industry Association (SNIA) an archive is "a collection of data objects, perhaps with associated metadata, [kept] in a storage system whose primary purpose is the long-term preservation and retention of that data."
Reading between the lines, the definition appears to say that an archive is not expected to be readily searchable. So, if your newsroom is looking for clips on the last elections, and last year’s video is in an “archive,” finding that content could take time. Some archive technology may make it difficult to know precisely where the desired video is located. Broadcast/production-focused archives typically provide databases of databases enabling keyword/metadata search functions. This helps users find the correct tape, but one still has to physically get and load the tape.
When considering a long-term storage solution, be sure you understand what solutions your application needs to provide. Making a mistake in selecting an archive/backup system could be an expensive, and perhaps, a career-changing experience.
This is the elephant in the room. Why bother with the cost and maintenance of an in-house backup/archive system at all? Let’s see what some vendors say.
Online backup services paint an enticing picture of the technology’s benefits: off-site storage, immediate access. Here are some other things to consider.
For content producers, the first consideration is security. Is the content secure? Can I be assured that only my corporation can access the material? Is the data encrypted?
Consider access speed. What bandwidth connectivity is needed to the cloud? Who pays for and maintains that link? Is it secure?
Reliability is key. What is the provider’s reputation? How long has the company provided professional services, and who are their customers? What “if” the company went out of business or was sued? What happens to your content?
These are crucial questions a content owner answers before handing off valuable media to another company for storage. Once a content owner enters into such an arrangement, he is no longer in control of that content. You are trusting someone else to store, manage and return your livelihood to you.
A brief word about optical. It is a reliable technology. Data stored on an optical disk may last 100 years. Optical costs more than tape. Optical storage solutions are less common than tape-based solutions. Optical may be a good solution in certain applications, but because it has a smaller user footprint, it may not have the long-term technology support that both disk and tape enjoy. That said, nothing beats optical for longevity.
Selecting a solution
Now it’s time to pick a solution. Will it be tape, optical, online or spinning disk?
Keep current production media on spinning disk. The solution could be a production video server or a set of networked NAS or SAN disks. The benefits include:
• reliable operation;
• fast access;
• commodity products (less expensive); and
• it's easily upgradeable.
Move less used material to slower disks such as SATA drives. Benefits include:
• reliable operation;
• lower cost drives; and
• it's easily networked.
Move historical content to an off-site or in-house tape or optical archive. Benefits include:
• high-density storage in a small footprint;
• lower power costs;
• large industry support; and
• long-lived storage media.
For more information on selecting archive and storage systems see these Broadcast Engineering articles:
File-based workflow, Part I
For long-term video archiving, tape is still king
How long will the archive last?
Scaling beyond SAN
Backing up critical data