Back-up tapes -Test the system frequently to ensure no data loss
Question:
How long are backup tapes good for?
Answer:
Always test your backups. Test them weekly or, better yet, right now. It’s easy, just create a couple of fake directories, place some files in it, and back it up. Now delete it from your server and try to restore it. That is critical.
The life of a data cartridge is typically measured in terms of end-to-end passes (the number of times the tape is coiled completely from beginning to end).
Lifespan is shortened by the storage conditions the tape is left in. Cartridges should be stored in their protective dust covers, in a clean and dry area, out of direct sunlight. Also, recorded media should be stored away from sources of stray magnetic fields in order to safeguard data from accidental erasure. Do not keep them on top of monitors.
Tape lifespan range depends on the type of tape. For example:
- 4 mm and 8 mm data cartridges are durable enough to withstand at least 1,500 passes with an archival life of up to 30 years. These should be replaced every 6-8 months depending on your tape rotation.
- DLT media is rated at 500,000 tape passes even under the worst-case temperature and humidity conditions. These are very durable tapes. They ensure positive data integrity and high reliability. These should be replaced once every 5-8 years depending on your tape rotation.
- QIC media minimum cartridge life is usually rated at 5,000 passes. Under proper storage conditions, it is recommended that tapes be retensioned (running the tape from beginning to end and then back again) at least once every six months to minimize the possibility of sticking, which could damage recorded data. It is recommended that these be replaced every 2 years.
Question:
What is cache?
Answer:
Cache, pronounced cash, is a special high-speed storage mechanism. It can be either a reserved section of main memory or an independent high-speed storage device. Two types of caching are commonly used in personal computers: memory caching and disk caching.
A memory cache, sometimes called a RAM cache, is a portion of memory made of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used for main memory. Memory caching is effective because most programs access the same data or instructions over and over. By keeping as much of this information as possible in SRAM, the computer avoids accessing the slower DRAM.
Some memory caches are built into microprocessors. The Intel 80486 microprocessor, for example, contains an 8K-memory cache, and the Pentium has a 16K cache. Such internal caches are often called Level1(L1) caches. Most modern PCs also come with external cache memory, called Level2(L2) caches. These caches sit between the CPU and the DRAM. Like L1 caches, L2 caches are composed of SRAM but they are much larger.
Disk caching works under the same principle as memory caching, but instead of using high-speed SRAM, a disk cache uses conventional main memory. The most recently accessed data from the disk is stored in a memory buffer. When a program needs to access data from the disk, it first checks the disk cache to see if the data is there. Disk caching can dramatically improve the performance of applications because accessing data in RAM can be thousands of times faster than accessing it on a hard disk.
Question:
What is the difference between an intranet
and an extranet?
Answer:
An intranet is a network of networks that is contained within an enterprise. An intranet uses TCP/IP, HTTP, and other Internet protocols and in general looks like a private version of the Internet. For many businesses an intranet provides a convenient central location for employees to obtain important information. Intranets can be used to publish corporate phone directories, employee information, sales, order status and tracking, corporate communications, and much more. Intranets allow internal information to be distributed quickly and are dynamic so information can be changed instantly and kept up-to-date so everyone has access to the most current documents. It is much easier and more cost-effective to update and replace one document on the intranet instead of updating, replacing, printing and distributing copies to everyone in the company. It may be entirely disconnected from the public Internet, but is usually linked to it and protected from unauthorized access by security firewall systems.
An extranet can be viewed as part of a company’s intranet that is extended to selected users outside the company. An extranet is a private network that uses the Internet protocols and the public telecommunication system to securely share part of a company’s private data with suppliers, vendors, partners, customers, or other businesses. Extranets provide a safe way to allow transactional business-to-business activities and can save your company time and money. For example, suppliers can receive proposals, submit bids, and even collect payments through an extranet site. It is typically behind a firewall, as an intranet usually is, and closed to the public, but is open to the selected partners, unlike a pure intranet. It requires firewall server management, means of user authentication, encryption of messages, and the use of virtual private networks like https://vpntap.com/ that tunnel through the public network.
Tech Q&A is provided by Entré of Brookfield. Small Business Times readers with questions can contract Entré at 414-938-2139 x3022, or via e-mail at dschm@pcsentre.com.
9-9-1999 Small Business Times, Milwaukee
