Prepress storage peripherals basics

Most people in the prepress area every day use a variety of different hardware, software, and intermediate media for storing data. For example, people can use Zip drives, 88MB SyQuest drives and small 730MB external drives to back up files.

With the rapid development of technology, these emerging terms and the storage media they represent, new technologies, and new products all make people feel at a loss and have no choice. These new memory storage files are getting faster and faster, and their prices are getting cheaper and cheaper.

Maybe you want to understand the difference between Ultra SCSI, Fast Wide SCSI, and SCSI2; What is the role of new products such as erasable CD and DVD-RAM in the printing industry? Maybe why are you not using SSA? (Continuous storage structure)? It first appeared in 1991, with obvious advantages but why did it not occupy the market? Even you have to ponder the question: What is the difference between a CD library, a CD changer, a CD array, a CD tower, and a CD jukebox? This article will briefly introduce some of the new terms and the new devices they represent.

First of all, let us review. The Lisa Mac, which was priced at $10,000 that year, actually dared to store all the information in the computing process with 1 MB of RAM and 10 MB of hard disk. Now it seems incredible. Now we understand what a computer with 10MB of storage is up and running, and no one will buy a new computer with less than 1.2GB hard drive. Zip is a built-in mass storage drive; SyQuests is an external mass storage drive; readable and writeable CDs cost less than $500; for most computers used for image processing, a 4GB hard drive is the lowest Configuration selection.

The development of storage technology is very fast. The first 40MB is quite a good hard disk drive. However, if a 2.1GB hard disk is installed on a new computer, it can only be regarded as a fairly common configuration, and a large-capacity hard disk drive It is rapidly spreading. CPU developers also have to take some changes to meet the development requirements of storage technology. For example, some operating systems do not recognize 2GB or more disk drives. Some existing external ports and buses limit the speed of information transmission. Without some basic knowledge, some of the special terms in the hard drive manual will make the manual difficult to read. As in the specification there are often some parameters, such as SCSI2 has 600,000 hours of average time between failures, running at 7200 rpm and only 10 milliseconds access time, and also has a conversion rate of 10MB/second. What do these numbers mean?

Drive connection

Although we only introduce SCSI here, it does not mean that we do not realize that there are a lot of IDE drives (even if it is also installed in the Mac). However, since many printing process peripherals are linked to SCSI interfaces, we talk about more SCSI here. And we will discuss some other new links at the end of this article.

SCSI (Small Computer Interface) was originally designed as an interface topology to extend the performance of peripherals connected to the CPU. Everyone who tries to hook up a peripheral with a parallel port has benefited from this common system. Those who try to hook up six devices on a single line will not be able to operate normally even if they use standard interfaces. Never use them without underestimating them.

The basic problem is the metal line. A SCSI connection has 25 pins and 50 pins. The metal wires connected to each pin may generate some noise and resistance. A broken connection is unusable, which is obvious, but if the length of the cable is too long, it may weaken the signal to the extent that it cannot work smoothly. Therefore, it is crucial to purchase some high-quality cables (gold plating will greatly change the situation).

The initial SCSI interface architecture allows information to be exchanged at 5 MB/sec. When SCSI provides two-way messaging, the application manages the device to send information in full bandwidth in one direction. Obviously, this data is not what you see when transferring files, it is the maximum possible transmission in one direction.

The SCSI2 device fills the compatibility issue by extending the standard to support richer command settings and doubling the bus speed to 10MB/sec. The next improvement is to increase the bus width from 8 bits to 16 bits, which in turn doubles the speed of the storage device. The fast wide-port SCSI2 configuration has now reached 20 MB/sec. The Ultra SCSI configuration doubles the clock frequency of the interface, so a fast SCSI setup can use an 8-bit bus to reach a rate of 20MB/sec, while a fast wide-port device can achieve a maximum rate of 40MB on a 16-bit bus. By using a dual-layer controller on Ultra SCSI, manufacturers of multi-disk arrays can achieve high-speed conversion of 80 MB/sec.

Another important reason to consider the use of Ultra SCSI is that it is particularly vulnerable to the cable and connector noise of all SCSI devices. Most SCSI tools are single-ended, meaning that each data line has an associated ground. In order to remove all noise generated so that it does not interfere with operation, the maximum cable length of the Ultra SCSI architecture is roughly limited to 10 feet. (Remember, this value includes the internal cable)

Keep in mind: When you plan to upgrade SCSI, you also need to install a card in the CPU to accommodate the wider bus and special structured drives. When taking into account the increase in speed, the increase in the cost is only the lowest effort. And different drivers are generally not more expensive than single-ended units.

driver

Assuming you have chosen the main hard drive, or choose it at the same time as you select the CPU, we will consider using this type of disk to handle upgrades, optimizations, and increased storage capacity. The most important factor regarding the operation of the drive is the machine wait time: the time the disk is used for rotation instead of reading or writing. The search time is in the order of milliseconds, which indicates the time from receiving the command from the read/write head to accurately locating on the disk. This waiting time is 100 times better than the electronic waiting time.

Another mechanical problem is the rotational speed of the disk, which is calculated in revolutions per minute. If you remember the phonographs spinning at 33 rpm, how fast they look when they accelerate to 78 rpm, you can imagine how fast the speed is at 5400 to 7200 rpm. Soon, this is just the most common speed. However, when you are waiting for a 650MB file transfer, it is still painfully slow. There are some new drive speeds on the market that can reach 10,000 rpm and a search time of only 8 milliseconds or less.

Of all the components that affect the speed of the drive, the search time and rotation speed account for 55% of the components. Followed by the disk transfer rate, or the speed of information transmitted to or from the disk, it is related to disk speed and density. Other factors that affect the drive speed are not related to the driver itself, such as the ability of the CPU to process information. Although you may be very careful to protect the drive so that its capacity does not appear too much fragmentation, it will take a while to save the information on a new drive, which is actually only a small part of the total speed flow .

Secure RAID

In order to ensure that the driver can work with maximum energy, you must find the bottleneck in the configuration and understand its performance. But this search will take a lot of time. With the price reduction of hardware, it is more economical to remove the old drive, add a fast wide-port SCSI card, and install a pair of fast wide-port drives in the RAID configuration. Of course, you have to select a different drive.

A redundant array of independent disks (RAID) simply combines two or more disks into one unit to work. You can combine a pair of 2GB drives into a fairly fast 4GB drive, or you can set up a network of drives to work for you. Companies like Mega Drive have made units that can hold 44TB or more of information. Although you may not need as much storage capacity as NASA, the requirements for storage capacity far exceed the power of 10MB in the early Apple computers.

RAID systems can be configured in many different ways depending on how information is used. If speed is the most important factor, the Striping (RAID level 0) format doubles throughput by writing two disks at the same time. If redundancy is the most important, you can write the same file to the same two disks (RAID Level 1). It will not increase speed, but it will protect your information, because if one drive is broken, the second drive still retains all the same data.

Speed ​​does not mean everything

When you select a storage medium, the type of information you are dealing with determines different options. A company that needs to access a small amount of information may choose RAID Level 5 for more efficient data conversion. It can independently read information, write to different disks, and allow read and write operations to take place simultaneously. This makes the data input-output exchange faster than the write speed. A prepress processing device that transfers information to a parallel port with large files generally uses RAID Level 3 for better throughput.

Among the factors that affect the complex, disk caching is another factor. Effectively cache the information stored in a storage block. Reading the cache ahead of time Assume that information adjacent to recently read information is quickly read and read in advance while waiting for other functional programs to run. There are many different types of cache available on the market to increase disk drive speed.

Removable storage media

There are many unexpected forms of removable storage media. Let's look at some of the most popular forms and changes that are already present or not noticeable.

Super floppy disk. There are many attempts to expect floppy disks to increase capacity and improve speed, although the only versions are the popular Zip drives, which can store 1,000MB of information and are inexpensive and portable. It's much faster than traditional floppy disks, but when you need to process information and use them, it's best to copy it to your hard drive and manipulate the information from there. Hard disk drives are faster, and Iomega also offers a SCSI accelerator card to speed up the drive.

Removable hard drive. Includes a variety of SyQnents and Iomega Jaz hard drives, which keep some small hard drives in a removable box. Capacity ranges from the original 44MB of SyQuest (though the drives are still in production but the drives are no longer manufactured) to the 1.5GB SyJet drives, which are relatively fast units if you can guarantee that the SCSI chain has not failed. We have heard people use Jaz and SyJet drives as boot disks, but it has not been recommended. I don't know if the war between SyQuest and Zomega is over. Even though most of SyQuest's competitive products have faster speeds and more capacity, Iomega certainly won all the battles.

Electromagnetic optical disk. The available 3.5-inch and 5.25-inch electromagnetic optical disks have 230MB to 2.6GB of storage capacity. They are much slower than hard drives, but the speed of the new write-through 5.25-inch unit is greatly accelerated, reaching a read/write speed of 8MB/sec, which is twice the original, making it more competitive. The 2.6GB high-capacity drive can also read and write the previous 630MB and 1.3GB standard media. Unlike the MO, the MO disk is double-sided, and its capacity is the sum of the two sides.

Phase change equipment. Panasonic produced this storage format. Although it won an industry's latest storage product award in 1995, it has not been popularized. This type of drive is too slow, but they have a double-layered function of reading and writing phase-change disks and reading CD-ROM disks at 4x speed. Although they cannot be used as a popular storage solution, we can still see advertisements under $200 (down from $600).