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Glossary of terms and references

BLOCKS

A block is a sequence of bytes or bits of data, which has a maximum length, called a block size. Data is written to and from the disk in blocks, rather than as separate bits or bytes, in order to speed up data transfer.

BUS/ BUSES

A bus is a collection of wires through which data is transmitted from one part of a computer to another. You can think of a bus as a highway on which data travels within a computer.

CACHE

A cache is a hardware or software component that stores data temporarily so future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation, or the duplicate of data stored elsewhere.

CERTIFY

Certifying is a process in which SoftRAID checks to ensure that the disk you're about to to use can reliably store your data. This kind of checking is something disk manufacturers don't do before the disk leaves the factory because of time and cost constraints. Read more about SoftRAID's certify feature here.

COMMAND LINE

The command line interface or window (known as the "Terminal" on the Mac) is a user interface where the user types in commands that are interpreted as instructions to the computer or computer applications (such as SoftRAID). For a user who knows the correct commands, the command line interface offers more control, and is generally quicker, than clicking through graphical user interfaces (which use icons and dialog boxes) with a mouse.

DISK

Digital (or hard) disk drives are block storage devices which contain spinning disks and movable read/write heads. Each disk is divided into blocks of storage—reading from or writing to disk happens at the granularity of blocks. There are two different motions occurring inside the drive. One is the rotation of the disks inside, the other is the side-to-side motion of the head across the disk as it moves between tracks.

DISK UTILITY

Disk Utility is the name of a utility on the Mac for performing disk-related tasks in Mac OS X. These tasks include the ability to intialize your disks, and to eraze all the data from them; for this reason disk utility should be used with great caution. Disk Utility can also be used to create RAID drives, but lacks much of the help and support SoftRAID provides for this, along with all the disk checking and monitoring features.

DRIVER

A driver (or device driver) is a low-level computer program that operates or controls a particular type of device attached to your computer, such as a disk drive mechanism. The driver driver communicates with the device through the computer bus (or communications subsystem) to which the hardware connects.

When a calling program (such as the SoftRAID application) invokes a routine in the driver, the driver issues commands to the device it controls—such as reading a block of data, in the case of a disk drive. The device can respond by sending data back to the driver, and in turn, the driver may then invoke routines in the original calling program—such as letting you know the data is correct.

In a hardware RAID system, the disks are controlled by the hardware RAID controller which can't be changed or updated; in the SoftRAID software RAID system, the driver replaces that controller and is constantly updated and improved.

Evaluation Period

When you first download and run SoftRAID or SoftRAID Lite, you can use it for free for 30 days to try it out. We call this the Evaluation Period. When SoftRAID is running in the Evaluation Period, all the features work, none of them are disabled.

Evaluation Period Expired

After you have been using SoftRAID or SoftRAID Lite for 30 days without entering a serial number, SoftRAID disables almost all features. While you can still mount your SoftRAID volumes and read and write files, almost all functions in the SoftRAID application are disabled. In addition, all RAID volumes are no longer protected from disk failure. For more information see FAQ page on expiry of the 30-day evaluation period.

FLASH MEMORY

Flash memory is an electronic (solid-state) non-volatile computer storage medium that can be electrically erased and reprogrammed. Non-volatile means that the memory retains data in the absence of a power supply.

SDHC

A Secure Digital High-Capacity (SDHC) is a (usually) tiny flash memory device used as removable memory for different digital devices such as digital cameras, video recorders, and computers. With SoftRAID you'll be able to check if the SDHC card you buy is faulty before you use it for recording your photos, videos, music etc.

MIRROR

A Mirror (RAID 1) volume is the safest RAID level you can have. It requires two disks so that all the files on one disk in your volume can be copied onto the other; if one drive fails your data is safe on the other. The disk which holds the initial data is called the primary, and the disk which holds the copy is called the secondary. If data on the primary disk changes, the mirror, or secondary drive will need to be updated so that its data is identical. SoftRAID's Monitor will warn you when that needs to be done. Read in more detail about Mirrors/ RAID 1 drives on the SoftRAID RAID levels page.

MOUNT

In order for you to access or use any kind of storage device (such as a hard drive, SSD, DVD, disk partition etc) the computer has to know where it is located in your file system. The location of the external device is known as the mount point. A user can only access files on any media that has an established mount point, known as 'mounted' media.

PARITY INFORMATION

Parity information is data that has been calculated from existing data in your RAID volume, and is used to recreate that data should it be lost through disk failure. For a full explanation (with pictures!) read about RAID 4 and RAID 5 on our RAID levels page.

PREDICTED FAILURE

SoftRAID can predict when your disks are more likely to fail. It uses SMART to watch the internal error counters for each disk. If these error counters indicate that a disk is more likely to fail, SoftRAID put up a dialog to get your attention. While testing disks in the SoftRAID Lab, we find that the SoftRAID correctly predicts that a disk will fail more than 50% of the time. The warning usually comes 1-4 weeks before the disk fails completely.

RAID / RAID levels

RAID (which stands for "redundant array of independent disks") is a data storage system that combines parts of two or more physical disk drives into a single volume. The purpose of creating a RAID volume is to provide greater data safety, performance improvement, or a combination of both. For a full explanation of RAID and RAID levels, visit our RAID levels page.

RAM

RAM—or Random Access Memory—is a form of computer data storage, installed in the RAM slots on the motherboard of your computer. Every time you open a program, it gets loaded from the hard drive into RAM. This is because reading data from RAM is much faster than reading data from the hard drive. Running programs from the RAM of the computer allows them to function without any lag time. The more RAM your computer has, the more data can be loaded from the hard drive into RAM, which can effectively speed up your computer. In fact, adding RAM can be more beneficial to your computer's performance than upgrading the CPU.

SECTOR

A sector is a specifically sized area on a hard disk or SSD. In a hard (magnetic) disk, a sector is a portion of a track. (A track is a circular path on the surface of the disk, where data is magnetically recorded and from which recorded information is read). Each sector represents the minimum storage unit of the disk - data can only be written to, or read from, a disk in multiples of the sector size. Most modern disks use 512 or 4096 byte sectors.

SERVER

A server is a computer that provides data to other computers (rather than interfacing with a human user via a screen and input device). The server can be providing data to systems on a local area network (LAN) or a wide area network (WAN) over the Internet.

Many types of servers exist, including web servers, mail servers, and file servers. Each type runs software specific to the purpose of the server. While server software is specific to the type of server, the hardware is not as important. In fact, a regular desktop computers can be turned into a server by adding the appropriate software. For example, a computer connected to a home network can be designated as a file server, print server, or both.

SMART

SMART (Self-Monitoring Analysis and Reporting Technology) was designed by IBM to monitor the status of a disk using various methods and devices (sensors). A single hard disk may have up to 30 such measured values, called attributes. Some of them directly or indirectly affect hard disk health status and others give statistical information.

Today most modern hard disks use SMART. Because it is not really a standard, the meaning of the attributes may be different from manufacturer to manufacturer. According the SMART specifications, when a problem is detected that signifies imminent disk failure, the hard disk should work for at least 24 hours to perform the data backup. But in many cases this time is not enough - that's why it is important to recognize problems and prepare before it's too late. SoftRAID uses SMART data to give you ample warning and help you ensure that no data will be lost because of disk failure.

SSD

An SSD or solid-state drive is a storage device full of memory chips that store data on integrated circuits (as opposed to magnetic disks). Data stored on an SSD is divided into blocks of data which can be electronically erased and reprogrammed. Most (but not all) SSDs use a type of non-volatile memory that retains data when power is lost.

Sometimes SSDs are referred to as disks although they contains neither an actual disk nor a drive motor to spin a disk. In fact, SSDs have no moving mechanical components. This distinguishes them from traditional electromechanical magnetic disks such as hard disk drives which contain spinning disks and movable read/write heads.For this reason, SSDs are typically more resistant to physical shock, run silently, have lower access time, and much lower latency.

STARTUP VOLUMES/ BOOT VOLUMES

You can use a section of your disk, or disks to create a volume which can be used to startup, or boot, your computer. A volume can be used as a startup/boot volume if it contains a full, usable operating system. Your startup volume can contain any operating system that can be used on your computer, such as OS X, Windows, Ubuntu, or any other operating system supported by your computer's hardware. You just have to ensure that the operating system is complete, that your computer allows you to boot from the volume, that the enclosure the volume is in (if any) allows your computer to boot from it and that the volume is correctly formatted. SoftRAID will help you to make volumes that you can use to start up your Mac.

STRIPES

Stripes are segments of data that are distributed across a number of disks. In a RAID volume, the data stripes are distributed across the disks in the volume. Depending on the system, data stripes may be created at the byte, block or partition level, and can be spread across all or only some of the disks in a volume (or disk collection in non-RAID systems).

The main advantage of disk striping is higher performance. For example, striping data across three hard disks would provide three times the bandwidth of a single drive. If each drive reads and writes at 200 MB per second, disk striping would, in theory, make available up to 600 MB per second for data reads and writes. However, if you are using a system that relies entirely on striped data (such as RAID 0), failure in any of the disks across which the data is striped will result in data on all the disks being lost. It would be like trying to make sense of a book where every second or third page is missing. With a SoftRAID RAID 4, 5 or 1+0 volume, striping data is done in parallel with either parity, or mirroring, in order to make volumes where access is fast, and data is safe from disk failure.

TILES

In the SoftRAID application, disks and volumes are represented as tiles in the GUI (Graphical User Interface)—one tile per disk or volume. Disks tiles are shown on the left, volume tiles on the right. Each disk or volume tile will show information and status of the disk or volume, and can be expanded to show more information.

TRIM

Data on an SSD is stored in blocks, which are, in turn, subdivided into pages of data. An SSD can only write to empty memory, and operates on a block level, even if the data it's dealing with is smaller than a block. For instance, every time you delete data from your SSD, even if it's only a page-worth of data, the whole block has to be deleted. So that the rest of the information in the block is not destroyed, it's copied into a temporary area, then put back into the block. It's like having to empty a whole shelf of books everytime you wanted to remove single book from a book case. This is not only extremely inefficient but the constant erase and rewrite actions will pile up and cause a fast wear of the flash memory chips that are found inside the SSD.

TRIM is a command that helps the operating system know exactly where the data you want to move or delete is stored. A TRIM enabled SSD is able to access data at the level of pages rather than blocks. Additionally, whenever a delete command is issued by the operating system or the user, the SSD automatically sends a TRIM command to immediately wipe the area of storage that holds the now-deleted data. This means that, the next time the operating system tries to write new data in that area, it won't have to waste time deleting it; it will already be empty. Essentially TRIM allows the SSD to manage its available storage more intelligently.

VOLUME

A volume contains defined portion(s) of a disk or disks which combine to operate as a discrete unit. A single disk can be part of one or more volumes and a volume can use all or part of one or more disks. A SoftRAID volume can use up to 16 disks. For more detailed about volumes and SoftRAID volumes, visit our RAID levels page.