The storage noun explanation of the computer hard disk

The disc of the hard disk is made from the surface of the disc that attaches the magnetic powder to the aluminum alloy (the new material also has to use glass), which is divided into concentric circles called "tracks". On each concentric track there is an infinite number of tiny magnets that represent the 0 and 1 states respectively. When these small magnets are affected by the magnetic force from the head, the direction of the Irresolute column is changed, and the magnetic force of the magnetic head is used to control the direction of the specified small magnets so that each small magnet can be used to store the total letter. The more small magnets on the 0 platter. The more information you can store.

The disc of the hard disk is composed of several platters (platter), which are overlapped together and placed in a sealed box, they rotate at a very Gao speed driven by the spindle motor, which rotates at a speed of 3600, 4500, 5400, 7200 and 10000 per minute. Inside the different hard drive, the number of its platters is not the same, a few two pieces, more than dozens of pieces. A platter has two sides, the number of the face from the fit side of the disc start, facing up on the side of the label is 0, the downward side of the label is 1. The 2nd disc faces up with a label of 2, faces down to 3, and so on. The hard disk has an electromagnetic read and write head on each side of each platter.

1, magnetic surface (Side)

The magnetic surface of a hard disk refers to the two sides of a platter. A magnetic field in the hard disk corresponds to a read-write head. Therefore, generally speaking in the hard disk read and write operation is no longer called the magnetic surface 0, magnetic surface 1, magnetic surface 2, but it is called Head 0, head 1, head 2.

2, Track (Track)

When the disk is formatted, the wave is divided into many concentric circles, and the concentric circles are also called tracks. The outermost track on the No. 0 side is numbered 0, 0, and the outermost track on the other side is numbered 1 0-way. The magnetic field of the hard disk generally has more than 3,001,024 magnetic inverses, as the track code increases along the center of the magnetic surface.

3. Cylindrical surface (Cylinder)

Concentric tracks with the same radius in the disc are called cylinders, which are the same set of tracks with the same number (position) on each disk, as shown in the figure. When the logical disk capacity of the hard disk is divided, the number of the cylindrical surface is usually not used.

The cylinder begins with the outermost cylinder, and when all the tracks of the cylinder have been used, move to a cylinder in the inner ring instead of saving a disc before saving one. The number of cylinders for the same series of hard disks is the same, but each cylinder contains a number of tracks that vary by the number of heads, calculated as: number of tracks = number of X-cylinders. such as the D740X,20GB model because there is only one head, so a cylinder of the director is a track, while the 80GB model is 4 heads, a cylinder is 4 tracks.

Take the outermost cylinder as an example, the outer ring track of the d740x has 837 sectors, and the maximum outer-ring cylinder capacity of the 20GB model is 1674kB for the 418.5KB,80GB model in terms of 512Byte per sector area. In other words, if the continuous storage of 500kB of data, 20GB hard drive will move the head to seek the road, IK80GB will not, just exist 冏 a cylinder head switch delay. People can think so, 80GB model of a cylinder equivalent to 20GB Model 4 cylinder, and the same cylinder track speed is usually faster than the switch between the cylinder, the 卨 data transfer rate is more favorable.

4, Sector (sector)

If each track as a ring, and then divide the 0 ring into a number of sector sectors, each sector is the disk access data, the most basic unit of a sector. The hard disk's magnetic surface and cylinder number are counted from 0, and the sector is 1, and each track contains an equal number of sectors. The director of a sector is often 512Byte, and the header of the sector contains the only one by one address mark 忐 ID of the sector, and the sectors are separated by gaps to facilitate identification by the system.

The number of slices that are divided into each track, and the size of the sector in the track varies depending on the type of media. For example, a 1.44MB floppy disk has 18 sectors, and most hard disks have more than 1763 sectors.

5, Capacity (Volume)

The disk's tolerances are determined by the number of cylinders, the head, the number of magnetic surfaces and the number of sectors. If each sector is 512Byte, its calculated formula is:

Hard disk Capacity (byte) = number of cylinders x head number x Sector x512 (byte)

However, when we say that the capacity of the hard disk is the number of megabytes (MB) or how many gigabytes (GB), this is referred to by the transformation of the Tung. The conversion method is: LKB=1024BYTE,LMB=1024KB,1GB=1024MB or LKB=1000BYTE,1MB=LOOOKB,1GB=1000MB. The more reasonable calculation method should be the former, but the hard disk manufacturer basically Tai s in the latter's total method as the unit, even some hard disk processing tool software also uses the latter transformation method. such as DM, such as 10000Byte as 1MB, so most software will be formatted hard disk after the report capacity may be lower than the manufacturer said. When purchasing a hard disk, the capacity of the hard disk is the first performance metric we should consider.

6. Speed per minute (Rpm,revolutionsperminute)

RPM refers to the rotational speed of the hard drive spindle motor (used to drive the disk). For example, "5400RPM" means the spindle speed of the hard drive is 5400 rpm (5400r/min) at 7 per minute. Work, the disk in the spindle phase of the video drive F, 卨 speed rotation, and the head arm in the voice coil motor control, the disk in the radial movement above, to address.

7. Average seek time (averageseektime)

Average seek time refers to the average time required for a hard disk to move to a specified track (should be a cylinder, tantric for a specific magnetic head) after receiving a read/write instruction. If there is no special description * to refer to the search time when reading, the unit is MS (milliseconds). In addition to the average seek time, there is also a way to seek time (Tracktotrack or cylinderswitchtime) and the whole seek time (fulltrack or Fullstroke), the former refers to the head from the current track above the adjacent track to the time required, The latter refers to the time required for the head to move above the most inner (or outer) circle track from the most outward (or most) circle track, and is substantially one times more than the average seek time. For actual work, we usually only care about the average seek time when buying.

8. Average Latency (averagelatency)

Average latency refers to the length of time that a specified read/write sector will be moved below the head when the head is moved to a specified track (the disc is rotated), and the faster the disc spins, the shorter the incubation period. Obviously, the average latency of a hard drive at the same speed is fixed, and the 7200r/min hard drive is about 5.556ms 4.167ms,5400r/min hard drive.

9. Average access Time (averageaccesstime)

Average access time is called average access time, generally in the manufacturer's published specifications will not be provided,-like a test score, which means the average time taken from a read/write instruction to the first data read/write, packet trichosanthes the average seek time, average latency, and related housekeeping time (such as instruction processing), As the internal operation time is generally very short (generally around 0.2ms), negligible, so the average access time can be approximately equal to the mean seek time + average latency, and thus the average addressing time. If the average seek time for a 5400r/min hard disk is 9ms, then theoretically its average access time is 14.556ms.

10, data transmission rate (dtr,datatransferrate)

The data transfer rate is per MB/s (megabytes per second, also called Mbps) or mbits/s (megabits per second, also called Mbps). DTR is divided into the largest (Maximum) and persistent (sustained) two indicators, according to the number of the junction with the 乂 and the internal data transmission rate. Internal DTR refers to the data transfer rate between the head and the buffer, and the external DTR refers to the data transfer rate between the buffer and the host (i.e. memory). External DTRH Limited depends on the interface of the hard disk, the current UltraATA100 interface (that is, representing the external DTR) the highest theoretical value can reach 100mb/s, continuous DTR depends on the level of the internal continuous DTR. Internal DTR is the real data transmission capacity of hard disk, in order to give full play to the internal DTR FFL, the external DTR theory value will be higher than the internal DTR, the internal DTR determines the external DTR of the real Ruan performance. Because the track on the outermost ring of the disk is ft long, the head is DTR more than the inner ring in the unit time, so the head is the most human inside the fi outer ring and the internal DTR is the smallest during the most internal drop.

11. Buffer Capacity (buffersize)

Many people also call caching (cache) Rong Dong, in megabytes. It is also written as Cachebuffer in some manufacturer's data. The basic function of the buffer is to balance the internal and external DTR. In order to reduce the host waiting time, the hard disk will read the data into the buffer first, and so on all read or buffer filled with the interface rate quickly to the main phase of l& send. With the advent of technology, vendors later added caching capabilities to SCSI hard disk buffers. This is mainly reflected in three aspects:

Prefetch (Prefetch). Experiments show that at least 50% of the read operations are read continuously in a typical case. The prefetch function simply says that the hard disk "privately" expands the reading range, after the buffer sends the specified sector data to the host (that is, the head has already read the specified sector), the head then reads a number of adjacent sector data and feeds into the buffer, if the subsequent read Operation IH good points to the adjacent sectors that have been fetched, To read directly from the buffer without head Gao, the access speed is raised.

Write Cache (writecache) 0 Usually, in the write operation, also sufficient: first write the data to the buffer and then sent to the head, and so on after the head is written and then report the host write finished, the host to start processing F-task. The hard disk with write cache is written to the host after the data is written into the buffer, so that the host can "liberate" in advance, and start to deal with other transactions (the remaining head write operation host do not wait), improve the overall efficiency. In order to further improve the effectiveness of the current manufacturers Lotus has applied a segmented caching technology (Multiplesegmentcache), the buffer into multiple/JH to store different write data, without having to wealth the entire buffer space for small data waves, but also can wait for all segments write full after the unified write, Better performance.

Read cache (Readcache). Temporarily save the read data in a buffer, and if the host is needed again, it can be provided directly from the buffer to improve read speed. Read caching can also use segmented technology to store multiple data blocks that do not 桕, and cache multiple read data to further improve the cache hit rate.

12. Noise and temperature (noise&temperature)

These two are not performance indicators. For noise, in the past, manufacturers have not cared, Tantric since 2000, due to market needs (such as OEM manufacturers want to produce quieter computers to increase the selling point), manufacturers began to use various means to reduce the hard drive noise, the ATA-5 Specification Third edition also joined the Automatic Acoustics (noise) management subset (AAM, Automaticacousticmanagement), so all new hard drives currently support AAM functionality. The noise of the hard disk mainly comes from the spindle motor and the voice coil motor, the sighs is also starting from these two points (the increase of the platter will also add noise). As for calories, every manufacturer has its own standards, and claims that the performance of the hard drive is what they expected, completely within the safety range, no problem. This is not the heart of a grandparent, but the key is that the hard disk is an integral part of its high fever will improve the overall temperature, perhaps the hard disk itself is OK, tantric may be around the accessories have been unbearable, others do not say, if the two hot hard disk installed very tightly, then bear nearly double the heat? So the calorific value of the hard drive still needs attention.