Posts Tagged ‘Disk’

SCSI Target

A SCSI Target is an "intelligent" storage device that acts as a ...


Be the first to comment - What do you think?  Posted by Greg - February 18, 2010 at 7:51 AM

Categories: Glossary   Tags: ,

Solid State Drive (SSD)

A Solid State Drive (SSD), in its simplest form, is a drive (disk) emulator, that uses solid state devices (memory) to store the data instead of using rotating magnetic platters. The memory used today could be volatile but it is backed up by a battery-based power system, or it could be flash RAM, that does not loose the data when power is removed.

Believe it or not, this is not a new technology.  Way back in the mid 1980’s, when I was working for an automatic test equipment (ATE) company, they designed and made a RAM Disk for a few select customers that needed to have faster load times of the data patterns that were used to test integrated circuits.  This was because the hard disks of that day were very slow when it comes to access time, usually in the hundreds of milliseconds.

Pros and Cons of Solid State Drives

The major benefit of solid state drives is speed.  This is because these drives eliminate the physical pieces of a hard disk that cause access delays.  When you read or write a block of data, the platter has to rotate into a position where that data block can be accessed, which takes time.  The actuator arm may also have to move the head across the platter, and that takes time too.  So any of these physical movements that can be removed will speed up the system.

There are a few other things that make solid state drives a good thing.  Since there is no physical pieces to move around, solid state drives are less susceptible to vibration in a computer system or storage array.  They are also less susceptible to changes in temperature.  A standard disk drive has to recalibrate internally whenever there is a temperature change of just a few percentage points.  That is no longer needed with SSD.

Speaking of power, solid state drives require less power than conventional disks, therefore making them part of the “Green Computing” or “Green Storage” movement happening today.

Now for the cons of SSD.  Cost is the biggest obstacle of using solid state disks.  But as the market evolves and they become more available to the general public, the price should come down.  Capacity is the other weak point of solid state drives.  To make a really big, really fast memory system is not that hard, but to make it fit into a form factor similar to what it is replacing, such as a 2.5 or 3.5 inch hard disk, then it becomes a challenge.

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Be the first to comment - What do you think?  Posted by Greg - January 18, 2010 at 2:42 PM

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Disk-to-Disk Backup

Disk-to-Disk backup, sometimes referred to as “D2D”, refers to the method of making a backup (of a hard disk or files on a disk).  What has been “normal” for years is making a backup to some kind of tape, or perhaps some other type of media (like a CD or DVD).

The main benefit of this method?  Speed!  When information is moved between to disk drives, it is much faster than having to deal with tapes or tape libraries.  This is because tapes usually have a limited capacity and have to be swapped in and out as the backup takes place, and as a result, tape backups are usually limited to times when the computer system that is being backed up is not very busy.  Now that many businesses, and the computers that drive them, run 24 hours a day, the time to make backups has become very limited and the faster you can make your backup, the better.

Another advantage with using D2D is that if and when some data has to be recovered, it can be done much faster.  This is because disk drives are “random access” devices (unlike tapes) and just the portion of the data that you want to recover can be found quickly instead of starting at the beginning of a tape and having to find that same information by reading from the beginning to the end of the tape.  Even if the tape is indexed and the drive can “fast-forward” to the correct record, it is still faster than having the backup on a disk.

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Be the first to comment - What do you think?  Posted by Greg - January 16, 2010 at 5:00 PM

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