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August 2000
Super Storage Guide
By Lowell Rapaport and Maria Medina
As revolutionary as developments such as storage area networks, network attached storage and Web-enabled administration may be, things are changing just as rapidly and dramatically at the hardware level. Technology is responding to the insatiable demand for speed and capacity with ever-faster, more capacious arrays, jukeboxes and libraries designed for mass storage.
Document-intensive applications have long relied on near-line storage solutions for quick access to high-volume archival records. While magneto optical (MO) and large-format optical once dominated, more affordable choices are now available, including DVD and memory-in-cartridge tape libraries that offer fast access to data. As storage prices have come down, even RAID/tape combos have become an affordable alternative for mass storage.
In the pages that follow, we recap the latest trends in the dominant storage hardware categories: RAID, CD/DVD, MO and tape. Whether it's the latest RAID systems and controllers with speedy fibre channel connectivity, capacious 4.7 GB-per-side DVD-RAM, or the dramatically new Linear Tape Open format expected to ship later this year, mass storage has never performed so well or so affordably.
RAID Controllers & Subsystems
There is no doubt that RAID system vendors will continue to push speed and capacity ever higher while cost per megabyte sinks to new lows. Contributing to this trend are the latest hard disk drives, which have capacities as high as 73 GB and disk speeds as high as 15,000 RPM. These technologies are merely continuing the trends that have been in place in the storage market for years.
What new activities are RAID system vendors pursuing that will add value to their systems and better functionality for end users?
Many vendors are dealing in storage area networks (SAN). Some RAID vendors, such as EMC, are now better known as SAN vendors. A SAN incorporates RAID but also includes secondary storage, including tape libraries and storage management software.
Many RAID vendors are also pursuing network attached storage (NAS). "NAS will grow from a $150 million market today to $1.5 billion in four years," says Paul Chan, vice president of RAID vendor Legacy Storage Systems, Markham, Ontario.
Tape library and optical disc jukebox vendors are already adopting NAS as a way to add value to their hardware. The slower storage devices are not hampered by the performance of 100 Base T ethernet. RAID systems are another matter. High speed RAID systems are most effective when the computers running storage-intensive applications, like databases, are connected directly to the RAID. On a network, RAID systems tend to be either simple, low-end arrays using software-RAID and inexpensive IDE disk drives, or they are systems designed for high capacity, with many drives per controller and RAID 5 for redundancy.
For backup, network attached RAID systems may have integrated tape drives or high-speed fibre channel or SCSI interfaces dedicated to a tape autoloader or library.
Expect server clustering to go hand-in-hand with RAID system installations. Clustering allows servers to be redundant to each other and improves scalability by spreading the processing load over more machines. It is a natural extension of the redundancy found in RAID systems and implements well in SAN environments. As RAID vendors make SANs and storage management software more integral to their product lines, server clustering will also be offered out of the box.
RAID vendors may eventually separate into three groups: companies that sell SANs and more closely resemble system integrators; companies that remain RAID vendors with, perhaps, some ventures into network attached storage; and companies that deliver SAN integration services and SAN-capable equipment and NAS storage.
Buying RAID Controllers & Systems
RAID is a complex storage system that has many variables. Vendors provide
a wide variety of solutions that are geared to meet a buyer's needs. Here
are the finer points to selecting RAID subsystems.
1. Service/support options. Is the product backed by a warranty? How long
does it last and what does it include? What are the terms of the RAID supplier's
drive certification program? Will the supplier provide component replacements
in an emergency?
2. Host connections. What is the interface to the host computer, SCSI or
fibre channel? Or is it NAS? Choosing an interface will depend on how the
RAID system will be used. Is it for workstation storage, network storage,
or network file sharing?
3. Device interface. Are the internal connections Ultra SCSI or Ultra2
SCSI, wide or narrow, single ended or differential?
4. Hot-swappable components. Which components are hot-swappable - ones
that can be removed or replaced while the system is online and operating?
Look for hot-swappable power supplies, disk drives and fans.
5. Redundancy. What features are offered that offset possible failures
and ensure continuous operation? Look for redundant drive I/O channels,
host controllers, cooling fans and power sources. Some units also offer
triple redundancy.
6. Error or failure notification. Are there visual and audible alarms in
case of failure? Does the unit provide front panel controls and LCD indicators
for troubleshooting?
7. Cache sizes. Are there both read and write caches? Read caches improve
read performances overall, while write caches are especially important on
RAID 5, since each write requires accessing multiple drives.
8. Dynamic expansion. Can you add drives without downtime? Is it costly?
9. Subsystems vs. controllers and enclosures. What does your unit include?
Which controllers does it use? Is the enclosure tower or rack mount? What
is the mounting mechanism?
10. Controllers. Controllers can be mounted within the array or in the
server. Do they perform load balancing? Do they have automatic fail-over?
What is the fail-over time?
11. Controller drive ratio. Higher performing systems have fewer drives
per RAID controller. This puts less processing load on each controller,
permitting faster performance. Systems where a single controller supports
dozens or hundreds of drives are slower and are mainly designed for bulk
storage.
12. RAID channels. How many RAID channels does the controller support?
How many channels can each drive support?
13. Drives. How many drive slots are in each array case? How many drives
does each RAID controller channel support? Does the controller support a
hot spare drive? How many hot spares are supported at one time?
CD/DVD Jukeboxes
With all the developments in the 120 mm storage market this year, near-line storage has never been so affordable. As a result, more and more companies are switching to the format.
It's now almost impossible to find a CD jukebox that isn't upgradable to DVD. And why limit your options if you won't have to worry about reading your old discs?
"You can read all your CDs with a DVD-ROM, so why would you buy a CD drive," asks Mark Anderson, manager of 120 mm products at Plasmon, Eden Prairie, MN. "CD was restrictive. What was lacking was the economics of capacity. And then along came DVDs."
One of the most notable developments in the DVD market is the arrival of 4.7 GB DVD-RAM drives from Hitachi, Panasonic and Toshiba. Hitachi will start shipping its 4.7 GB drives to the mass market in August, according to spokesperson Werner Glinka. The DVD-RAM will match Pioneer's DVD-R format in capacity, both providing more than seven times the capacity of a CD (4.7 GB per side for DVD vs. 650 MB for CD, which is limited to single-sided recording).
DVD's exponential increases in capacity are growing even larger now that jukeboxes that can flip discs are becoming available. The disk flipping robotics let you unlock the storage capacity on both sides of the DVD disc, giving you 9.4 GB from a single slot - more than 14 times the capacity of a CD.
Currently, Asaca, Golden, CO, and Kubota, San Jose, CA, are the only manufacturers offering disc flipping capabilities. Pioneer, Long Beach, CA, plans to add the option by the fourth quarter.
With Internet data storage growing so rapidly, Glinka says these DVD innovations "will enable the next revolution of documentation." Imagine, he suggests, replacing text and diagrams with video product manuals that show how to assemble a product.
So how does DVD impact other storage markets, such as tape and magneto optical? Anderson believes users of low-end tape products will be attracted by the inexpensive storage possibilities of DVD.
"Tape itself is cheap," says Anderson, "but tape automation devices are expensive."
Anderson contends that DVD has not negatively impacted magneto optical. "DVD can't replace MO in a typical MO application," says Anderson, adding that archives subject to legal and regulatory requirements demand more robust technology.
Buying CD/DVD Jukeboxes
Here are 9 features to consider when choosing a CD/DVD jukebox.
1. Format. If you're considering DVD, look for the new 4.7 GB DVD-RAM (rewritable)
drives (up from 2.6 GB per side). If you demand a nonrewritable solution
and universal readability in all DVD-ROM drives, consider Pioneer's DVD-R
format, which also has 4.7 GB per side.
2. Disk flipping. Disk flipping, an option in some DVD jukeboxes, lets
you access a whopping 9.4 GB per disc - double the capacity of CD-derived
jukeboxes.
3. Media exchange time. The speed of the robotics and the distance traveled
inside the jukebox figure in the average media exchange time. Dual pickers
can also increase exchange times.
4. Capacity. Determine your storage needs. Are they at the low end (30
GB to 500 GB), midrange (500 GB to1.0 TB) or high end (more than 1.0 TB)?
Plan for growth and an extra cushion of capacity.
5. Capacity vs. speed. Is your primary concern maximizing storage or minimizing
retrieval times? This will help you determine your disc-to-drive ratio.
If you have many users, having more drives will help ensure fast availability
of data.
6. Size of the cache. A jukebox with a large cache dramatically lowers
retrieval time for frequently accessed documents. Network attached storage
devices can also add additional cache.
7. DVD and CD support. Does the jukebox support DVD-RAM, DVD-ROM or DVD-R
drives? Since multiread DVD drives also support CDs, both types of media
can be stored in a DVD jukebox.
8. Modularity. Is the jukebox flexible enough to allow upgrades to faster
or higher-capacity drives? Can you switch from CD to DVD drives? Can you
easily swap out drives for discs or vice versa? Most jukeboxes offer different
configurations that allow you to expand the number of drives or disc magazines
as your storage needs change.
9. Hot swapping. Some jukeboxes allow for single disc loading through a
mail slot or batch loading of magazines while the unit is online.
Magneto Optical Jukeboxes
When storage is subject to regulatory standards - either from the Food and Drug Administration, the Securities and Exchange Commission or some other regulatory agency - there's no match for the reliability and assurance of magneto optical (MO) storage. Most MO media has a rated shelf life of 30 years or more, its data delivery speed is unequaled, and WORM (write once, read many) options give you the assurance of storage that can't be erased.
The MO jukebox market has been stable over the last year, with only one new model introduced - the 24-slot, 125 GB, 125ex from market leader Hewlett- Packard, Greeley, CO.
Recent advances in the DVD market have led to talk of MO being outmoded, but Mark Anderson, manager of 120 mm products at Plasmon, Eden Prairie, MN, says this isn't the case.
"MO is not growing rapidly, but it is consistent," Anderson says. "A lot of people would like to believe that MO will be impacted [by DVD], but it hasn't been. MO is the Indie 500 of the storage market."
Anderson alludes to MO's data seek time, which is 25 milliseconds vs. 210 milliseconds for DVD-RAM. MO's data transfer rate is also faster at 2.9 MB/sec vs. only 1.38 MB/sec for DVD-RAM. In layman's terms, MO finds and delivers data faster than DVD and faster still than CD or tape.
A near doubling of capacity is also expected for magneto optical. Sony, San Jose, CA, the leading MO drive supplier, expects to debut the next generation of 9.1 GB-per-disk drives by early next year. As in the past, most jukeboxes should be field upgradable to these higher-capacity drives and disks, yet you'll still be able to read older-generation media.
Buying MO Jukeboxes
Here are seven issues and features to consider when purchasing MO jukeboxes.
1. Capacity. Can you add more disks as storage needs increase? Many MO
jukes are modular and can be upgraded.
2. Cost. Don't just look at the cost of the hardware. Software, installation
and service contracts can add up.
3. Cartridge-to-drive ratio. Look for a low ratio or the option of adding
more drives as the number of disks increases.
4. Robotics. Does the unit use single or dual pickers? As with 120 mm jukeboxes,
dual pickers reduce swap time by carrying two disks at once.
5. Access to data time. What is the mean time required for delivering data?
Read time provides a better comparison between jukeboxes.
6. Reliability. Along with robotics ratings of MSBF (mean swaps between
failure), also look for a high drive MTBF (mean time between failure) rating.
Determine what service and support options the manufacturer offers.
7. Compatibility. Is the unit forward and backward compatible? Can your
unit be easily upgraded to the 9.1 GB drives due out next year?
Tape Libraries
Despite being the oldest mass storage technology still in use, tape is exhibiting the most activity in terms of new technology. New developments in the tape library industry include increased availability of network-attached storage, more advanced library controllers, and most importantly, new tape formats.
This year two completely new tape formats - super digital linear tape (SDLT) and Ultrium - are in the works. Both technologies use the same single reel half-inch tape form and both are poised to take over the lucrative digital linear tape market.
Each has advantages. SDLT will be backward compatible with existing DLT tape making it a clear upgrade path for current DLT users. SDLT tape drives will be sold by Quantum and Tandberg and will be compatible with tape libraries already designed to use DLT tapes. Ultrium is the result of the Linear Tape Open (LTO) project being developed by IBM, Seagate, Hewlett- Packard and Fujitsu. Ultrium enjoys broad industry support from some of the biggest names in enterprise computing. Ultrium tapes are slightly smaller than DLT and SDLT tapes. This may permit somewhat higher slot counts in larger tape libraries.
The developers of SDLT and Ultrium had said that the tape drives would be in production during the first half of this year. However, as of this writing, no coming-out date had been announced.
No delays are affecting the availability of network-attached tape storage. Library manufacturers like ADIC and Grau have already introduced network-attached tape libraries of varying complexity. Some use simplified thin servers while others, including Grau, are using dedicated Windows NT servers with archiving software and RAID systems as cache.
Network-attached storage has many advantages. Media management is handled by the device, usually through an easy-to-use cross-platform Web interface. By incorporating library management in the storage device itself, network-attached storage technology eliminates the need to buy a separate library management system. There are also pitfalls to NAS storage: The devices tend not to be very expandable and their thin servers are only designed to run a single library at a time. If you need to add additional slots, you may have to buy a second NAS tape library.
Helping to simplify library management, some manufacturers are developing more advanced library controllers that can be managed over a corporate LAN using ordinary Web tools. The most notable is the new Spectra 12000 tape library from Spectralogic. Instead of a handful of cryptic buttons and an LCD display, the library uses a Windows CE computer with full graphical user interface and color display. The controller has its own Web server giving the library some of the same management functions found in network attached devices. Similar controllers have been developed for DVD jukeboxes by Asaca.
This level of control will be a big advantage as library manufacturers move
from traditional server-attached storage architectures to network-attached storage
and storage area networks. They separate library management from the need to
move data in and out of the library, features previously only available in the
largest libraries from StorageTek and ADIC. In time, we should expect to see
tape libraries gain not only higher capacities but brains as well.
Buying Tape Libraries
Here are the important questions and issues you should address when purchasing
tape loaders and libraries.
1. Network or host connections. Which interface does the library use? Can
the library be connected to a SAN? Will it support serverless backup? Is
there a network attached storage option? Is it compatible with your network?
Does the library support multiple host connections?
2. Drives. How many drives does the library offer? High drive-to-tape ratios
allow for faster or simultaneous backup processes and access to data. Are
the drives hot-swappable, thus eliminating downtime? Will an upgrade to
newer tape formats be possible?
3. Capacity. The listings in the accompanying tables are in native capacities.
Note that many manufacturers quote capacities with 2:1 compression ratios.
4. Scalability. Can you combine multiple libraries to expand capacity as
your storage needs increase? Can you increase the number of drives or magazines?
What do upgrades cost?
5. Robotics. Once you've selected a few models to choose from, compare
average robotics move time and average drive load time.
6. Fixed or movable barcode readers. Is a barcode reader standard or optional?
Barcodes on the tapes decrease the time needed to find data. Moveable barcode
readers decrease wear on the tapes by scanning them while the cartridges
are still in place.
7. Reliability. Look for high MTBF (mean time between failure) drive ratings
of 250,000 hours or more and high MSBF or MCBF (mean swaps or cycles between
failure) robotics ratings of 1 million or more.
8. Service/warranty. What warranty, service and support options are included?
If the library manufacturer is using another company's drives, who supports
them? Does the company offer a guaranteed uptime?
9. Loading features. Can magazines be loaded through a mail slot, allowing
for the addition and removal of tapes without opening the library, which
can expose it to dust? Are there security controls for loading and removing
tapes?
Large-Format Optical Storage
Not included in the magneto optical jukebox table are listings for 12-inch WORM. Just one company, Plasmon, is seriously developing large-format optical technology. Despite its status as the only player in the market, Plasmon has proven its commitment recently by introducing a new disc drive and a new autoloader.
The LM8000 increases 12-inch optical capacity to 30 GB per disc, more than double the previous generation's 12 gigabytes. The new drive is also dual headed, so all 30 GB are available at once with no disc flipping required. To achieve the same performance with 5.25-inch MO would require 12 separate drives at 2.6 GB per surface. According to Plasmon, this is an advantage to companies that need availability to data for a large number of users at once, such as in customer service environments.
Almost all large-format optical drives are sold in automated systems. Previously available were 6-slot autoloaders and 61- and 141-slot jukeboxes. Earlier this year at the AIIM show, Plasmon introduced a 12-slot robot that can be fitted with one or two drives. This library makes up to 60 GB available online with an additional 300 GB near-line. A 5.25-inch MO jukebox would have to hold 23 to 24 drives, a feature that is not available in any but the largest libraries. This makes 12-inch optical competitive for users who need a lot of removable storage online but don't necessarily need a large jukebox.
Plasmon's large format optical is not for everyone. The drives cost $29,000 each and libraries only reach 4.2 TB in capacity. Tape libraries can accommodate much larger archives and 5.25-inch MO is much less expensive overall. But for select users who need the security of WORM technology and the online performance of a RAID system, Plasmon's large format fills an essential niche.
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