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Sunday, March 2, 2008



Digital content is all-pervasive in today’s society, from MP3 files to home movies, not to mention the multitude of financial, e-mail, household or business records typical consumer keep on their PC. The explosion of all of this digital information is rapidly consuming available hard disk drive (HDD) space and creating a critical storage challenge. This proliferation of digital data that consumers want to store is the driving force behind external storage.

The available options
Some of the popular external storage solutions are:

Optical storage: One compact disk can hold around 700 MB of data. Move forward to a DVD, which can house more than 4.7 GB of information. DVDs store information in the form of simple, steep-sided pits, each holding 1 bit of data. Although the storage capacity can be increased by writing the pits into different layers of the disk, it is still currently limited to around 4.7 GB per layer. In fact, researchers in Switzerland, Greece and UK are developing an optical storage method that could squeeze one terabyte of data onto a DVD-sized disk. Their angular multiplexing technology is backwards compatible with existing DVDs and CDs.
Another step forward is the Blu-Ray format supported by companies like Sony, Hitachi, LG, Philips and Samsung. This has now come to life in the form of Blu-Ray disks having a capacity of around 27 GB.

Zip drives: A zip drive is a removable storage device that securely stores all your important computer data, magnetically. It uses removable disks (Zip disks) to store hundreds of megabyte of data. Zip disks, and about twice as thick. Companies like lomega are coming with drives that can hold 100 or 250 MB to 750 MB of data. Because they’re relatively inexpensive and durable, they have become a popular media for backing up hard disks and for transporting large files.

External drives: External hard disk drives were developed to give consumers the freedom to be mobile and carry their data with them. In the present market scenario, external storage drives are being extensively adopted by the SME/SOHO segment and also by individuals who are creating digital content. External HDDs score over internal HDDs because of portability, economy and flexibility. They are excellent solutions for safe and effective backup, and also for additional storage requirements.
There’s a close competition between Seagate and Maxtor in this segment. Seagate has introduced the world’s first USB2 pocket drive along with the portable external hard drive (offers up to 100 GB). Their latest drive comes with 400 GB capacity. Maxtor, too, has recently launched their OneTouch family of products. “With capacities ranging from 80 GB to 300 GB, the product allows the user to store their data in a single device instead of storing it in multiple devices,” says Yogesh Kamat , sales manager, Maxtor.

Just a Bunch Of Disks (JJBOD): If you have some disks in a system that you decided not to configure into a RAID array, what do you do with them? Traditionally, they are left to act as independent drive volumes within the system, and that are left to act as independent drive volumes within the system, and that’s how many people actually use multiple drives in a Pc. In some applications, however, it is desirable to be able to use all these disks as if they were one single volume. The proper term for this is spanning (also called ‘Just a Bunch Of Disks’ or JBOD). If you have a number of odd-sized drives, JBOD will let you combine them into a single unit without loss of any capacity. A 10 GB drive and 30 GB drive would combine to make a 40 GB JBOD volume but only a 20 GB RAID 0 array.
JBOD actually combines drives into larger logical volumes. It provides no fault tolerance, nor does it provide any improvements in performance compared to the independent use of its performance compared to the independent use of its constituent drives. (In fact, it hurts performance, by making it more difficult to use the underlying drives concurrently, or to optimize different drives for different uses).

RAID: Short for Redundant Array of Independent (or Inexpensive) Disks, RAID stands for a category of disk drives that employ two or more drives in combination for fault tolerance and performance. RAID disk drives are used frequently on servers but aren’t generally necessary for personal computers. Fundamental to RAID is “striping”, a method of concatenating multiple drives into one logical storage unit. Striping involves partitioning each drive’s storage space into strips that may be as small as one sector (512 bytes) or as large as several megabytes. These stripes are then interleaved round-robin, so that the combined space is composed alternately of strips from each drive. In effect, the storage space of the drives is shuffled like a deck of cards. The type of application environments-I/O or data intensive-determines whether large or small stripes should be used.
There are a number of different RAID levels, starting from Level 0 to Level S. RAID-0(Striped Disk Array without Fault Tolerance) is the fastest and most efficient array type but offers no fault-tolerance. RAID-1(Mirroring and Duplexing) is the array of choice for performance-critical, fault-tolerant environments. In addition, RAID-1 is the only choice for fault-tolerance if no more than two drives are desired. RAID-2 (Error-Correcting Coding) is seldom used, since ECC is embedded in almost all modern disk drives. RAID-3 (Bit-Interleaved Parity) can be used in data intensive or single-user environments that access long sequential records to speed up data transfer. However, RAID-3 does not allow multiple I/O operation to be overlapped and requires synchronized spindle drives in order to avoid performance degration with short records. RAID-4 (Dedicated Parity Drive) offers no advantages over RAID-5(Block Interleaved Distributed Parity) is a good choice in multi-user environments, which are not write performance sensitive. However, at least three, and more typically five drives, are required for RAID-5 arrays.

TAPE DRIVES AND LIBRARIES: The significance of tape as a storage medium cannot be doubted. It remains the technology of choice in large and small business for archiving data records. There are seven ways in which you can lose data: human error, hardware and software error, natural disaster, electricity problems, theft/ sabotage and viruses. Tape is the only medium that offers protection against all seven.
Tape storage is required for long-term storage purposes and for backing up online data. Such storage is getting more and more automated, wherein drives are equipped with robotic arms. Data is downloaded off the disk sub-system and stored on tape, a much more affordable media. DLT, LTO and SDLT are some of the widely used tape technologies. These have become the favourites in the mid-market space and cater to the speed and capacity requirements of most customers. LTO Generation 2 is considered pretty fast while Magstar scores in terms of data integrity.
High-end customers generally opt for automated versions of tape libraries since these manage terabyte of data that are sitting inside the corporate data center. The tape libraries are used to duplicate data sets and have one set shipped offsite. These libraries often scale to as much as 190 drives in the same machine. The number of tape categories slots that come with these varies from 20 to 60. The SME space usually goes in for internal tape drives as well. All these solutions usually go hand-in-hand with software for automation.

SAN, NAS AND DAS: Direct-attached storage, or DAS, is the most basic level of storage, in which storage devices like drives are part of the host computer or directly connected to a single server, as with RAID arrays or tape libraries. Network workstations must therefore access the server in order to connect the storage device. This is in contrast to networked storage such as NAS and SAN, which are connected to workstations and servers over a network.
Network-attached storage, or NAS, is a special purpose device, comprising both hard disks and management software, which is 100 per cent dedicated to serving files over a network. A server has the dual functions of the sharing and application serving in the DAS model, relieves the server of storage and file serving in the DAS model, potentially causing network slowdowns. NAS relieves the server of storage and file serving responsibilities, and provides a lot more flexibility in data access by virtue of being independent. It is an ideal choice for organization looking for a simple and cost effective way to achieve fast data access for multiple clients at the file level. Implementers of NAS benefit from performance and productivity gains.
A storage area network (SAN), on the other hand, is dedicated, high performance storage network that transfer data between servers and storage devices, separated from the local area network. With their high degree of sophistication, management complexity and cost, SANs are traditionally implemented for mission-critical application in the enterprise space. In a SAN infrastructure, storage devices such as NAS, DAS, RAID arrays or tape libraries are connected to servers using fibre channel. In contrast to DAS or NAS, which is optimized for data sharing at the file level, the strength of SANs lie in the their ability to move large blocks of data. This is especially important for bandwidth-intensive application such as a SAN also enables it to offer higher levels of performance and availability than any other storage medium today.

ONLINE STORAGE: An online storage service lets you save files online. If you have Internet access, you can get your files from the online storage site whenever you need them. This can be handy if the company’s servers go down or if the company goes out of business. Most online service providers may charge a monthly fee for the usage of a particular amount of disk space. Online storage implies redundancy and outstanding security along with anytime-anywhere access and easy file sharing with your friends. Sites that offer virtual hard drive space let you access those files anytime, from anywhere in the world, no matter what happens. Recently, Caddy Data Services has been offering solutions that address the secured data archiving, data mobility and continuity needs of the individual and the SME market in India.

It makes more sense to deploy an external storage sub-system on a long-term basis, since it gives the organization implementing storage expansion to go in for the various options available. External drives are much easier to install than internal drives inside a PC. But this requires knowledge about installing a new drive and connecting a new drive and connecting new cables, and in some cases, a new controller card and the re-configuration of new software.
“A far easier approach is to plug in a disk drive specifically for external storage-one that can sit atop the desktop. This does not require the end user to open the PC,” Not only is this external drive simpler to install, but it also has the advantage of transferring lots of data from one computer to another. An external drives can also serve as a back-up copy that can be kept in remote location, in the event the original data is damaged or lost. Currently, sales of external hard drives for PCs are doubling every year, outpacing that of internal drives.


Globally, the trend is towards storage consolidation, but in India, the scenario is totally dependent on the needs of the organizations. DAS solutions have the largest market share and storage consolidation, while SANs are picking up, according to S.R.Prasannakumar, senior product manager, Xserve India. In most cases, SOHOs, SMBs and SMEs are still looking at DAS as a viable external storage option, unless they have to adhere to certain global standards for data security due to parent company policy or business need. In that case a SAN solution would be looked upon as a external storage solution.
Also, the mid-tier segment is increasingly being seen as a huge market for external storage solutions, and vendors are gearing up by launching specific products and solutions to tap this immense potential. Over the past one year, EMC Corporation has launched 17 products, out of which 11 were specially targeted at SMBs. Since the SMB segment is highly price-sensitive, there is a trend towards cost reduction without compromising on the feature. Some of the trends as per a EMC spokesman are:
§ NAS-SAN convergence: A strong trend in the storage market where customers are moving towards an environment where both NAS and SAN co-exist.
Most customers do not want to replace their SANs (on which mission-critical applications like ERP, databases and CRM run). However, they would like to add
§ NAS-like flexibility to their SANs. Many vendors like EMC offer products that enable NAS and SAN convergence.
§ The technology that is revolutionizing NAS is NAS gateways. These are essentially NAS headers that allow NAS functionality on a SAN.
§ Gateways are the fastest growing segment of the NAS market .in fact, NAS gateways combine with SANs to offer comprehensive networked storage solutions.
§ R&D growth in software: India is coming up strongly as an R&D hub for software. This will fuel the faster evolution of NAS.
§ Cost reduction:
§ The SMB market is extremely price sensitive in India, and the vendors are lowering the price barrier. The future will see further reduction of price, hence boosting the SMB storage market in India.

The number of external storage devices in the market continues to proliferate, but not all of them are user friendly, flexible and affordable. Some external storage solutions are optical storage ,Zip drives, External drive, Tape drive & Libraries, On-line storage.


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