How To Determine Hard Drive Physical Size

Hard Drive 101

How does a hard drive work?

drive platter

Effigy 1 The inside of a difficult disc drive, showing the disk platter and the read/write head.

While the deejay platter looks like a mirror, it's actually composed of upward to trillions of tiny magnets standing on end, arrayed in concentric circles. The polarity of each magnet can be "up" or "down," which indicates whether the bit is a i or a 0. The read/write head moves like a record tone arm, and can flip the polarity of the magnet when it's writing data, or read the polarity when it'southward reading data.

The magnets in a hd are organized in concentric circles — as many as 250,000 rings on a iii.5-inch platter. The head skims back and along at upwards to 10 meters/second and must terminate on a line 1/10 the width of a human hair, and then correctly read the polarity of each bit. It'south amazing that this is fifty-fifty possible, and even more than astonishing that it'south affordable.

A difficult deejay drive also has electronics to command the mechanism, to translate the data to a format that can be written to the disk and to practise error correction and analysis. Hard drives have a power connector that provides juice for the motor that spins the drive and for the controller circuitry. Each bulldoze also has a data interface: IDE/ATA or SATA for desktop drives, and Serial Fastened SCSI (SAS) or Fibre Channel for enterprise drives.

Hard bulldoze sizes

Hard drives come in two basic physical sizes: 2.v-inch and 3.five-inch. These sizes refer to the size of the data platters, non the size of the hard drive machinery. Traditionally, ii.five-inch drives are used for laptops while 3.5-inch drives are used for desktop computers. Some meaty desktops also use the smaller drives to enable a smaller grade gene for the reckoner.

3.5 and 2.5 inch drives

Effigy iishows the ii sizes of drives generally in use. three.v inch drives, on the correct, are used in desktop computers and in freestanding storage devices. ii.five inch drives are used in laptops and portable storage devices. Newer 2.five inch drives are also being used in high-performance storage devices.

2.v-inch drives more often than not spin slower which ways that they have slower information throughput. They as well have a smaller data chapters and are more expensive per gigabyte. The smaller drives practice have several advantages depending on the use.

They are physically smaller then they tin fit in laptops and small-scale portable enclosures.

They may accept meliorate "seek" times, since the read head has less distance to travel than with a larger bore bulldoze.

They need less power to spin then they can by and large be bus-powered, pregnant they tin depict ability from a laptop without the utilize of an external power supply.

And since they are designed to be portable, most of them do a meliorate chore of "parking the heads" than full-size drives do. This means they are better able to survive being shipped around or used in a moving environment.

Recent developments in 2.5-inch drives are changing how the small-scale drives are used. A new class of two.v-inch high-speed drives has emerged that can be used in enterprise and server environments. At the moment these drives are very expensive per gigabyte.

Solid-state drives (SSD)

SSD

Figure iii Solid-state drives hold a number of advantages over spinning disks.

A new kind of storage device for computers has shown upward in the market over the terminal several years. Instead of spinning disks, solid-state flash retention is existence used as main storage. It offers a number of advantages, peculiarly for use in portable computing, and for speeding up sure kinds of data storage and access.

Difficult drive capacity

The capacity of a hard drive refers to the amount of information it can hold. These days, capacity is measured in gigabytes or terabytes. Due to marketing reasons, the capacities listed on drive specifications may not exist calculated in the aforementioned manner that your operating system calculates data sizes.

For instance, a drive sold as "500GB" actually but contains 465GB (really, the 500 number is gibibytes, and the 465 number is gigabytes. Aren't you glad you lot asked?) Windows continues this do, just Mac OS 10.six and later inverse the fashion it calculates size to match manufacturers' exercise.

For well-nigh notwithstanding photographers, we generally suggest that it'southward meliorate to get the largest capacity drives you're likely to need, at least for the side by side 6-12 months (if yous're on a RAID system, you'll want a longer time frame — possibly two years — due to the complexity of upgrade). Running fewer drives saves on space, power draw and heat generation. It'southward also easier to manage your drives if there are fewer of them.

For loftier-volume photographers and videographers, the consequence can be significantly more complex. Storage needs for individual projects will easily climb to hundreds of gigabytes or into terabytes. If you lot are in this situation, acquiring hard drive capacity may resemble the model that was used dorsum in the days of record or movie stock. Instead of keeping a general annal, you may take to factor the price of storage into the price of each project, and buy the drives/record/discs on a per-job basis.

It's also possible that you lot need to get to a Storage Expanse Network (SAN) model for storage, where enterprise-class servers manage a large tiered storage pool.

Should I use big drives or small drives?

One question comes up over and over. Is it improve to have your master storage on (fewer) bigger drives or (more) smaller ones? If y'all chose big drives, a unmarried bulldoze failure tin can take out a lot of files, and so information technology might seem like you go more protection with a larger number of smaller drives. We don't agree.

All your digital storage should be configured and then that failure of whatsoever one drive does not kill the but copy of any files. Y'all must backup the images to an boosted device if you want to preserve them.

If you lot use a smaller number of larger drives for storage, y'all will simplify the process of keeping rails of the drives, besides as the process for periodically checking on the integrity of your data. You'll too utilise less energy to keep them spinning and save on storage or desktop infinite. Additionally, larger drives are likely to be newer and faster.

Hard drive rotation speeds

As part of its specifications, each hard bulldoze has a speed at which the platter rotates, measured in RPMs. The faster the drive, the faster the throughput, since the head reads and writes the bits at a faster rate.

two.5-inch consumer drives typically spin at 4200, 5200, 5400 and 7200 RPMs. 7200 RPM drives are a proficient option at the moment, but sometimes 7200 RPM drives have likewise large a power draw or generate too much heat for the portable devices in which they are housed. The enterprise-form 2.5-inch drives currently spin at 10,000 or xv,000 RPMs.

three.5-inch drives generally come in 5200, 7200, 10,000 and fifteen,000 RPM models. The 7200 RPM models are good all-purpose drives and have the largest capacities. The faster drives are generally used for system or scratch disks, where fast deejay-swapping speeds up the performance of programs like Photoshop, which often accept to work with large files.

You lot can also purchase variable-speed iii.v inch drives, typically sold as "energy-saving" or "green" drives, running between 5400 and 7200 RPMs. These drives use less free energy and accept slower data transfer rates. This makes them a reasonable choice for Athenaeum and for off-line backups.

Hard drive interfaces

Hard drives come with one of several unlike connectors built in. When you buy a drive, it will specify which one is built into the drive. The five types are ATA/IDE and SATA for consumer-level drives, and SCSI, Serial Attached SCSI (SAS), and Fibre Channel for enterprise-class drives.

ATA/IDE Cablevision

For many years, Avant-garde Engineering Attachment (ATA) connections were the favored internal bulldoze connection in PCs. Apple adopted ATA with the Blue and White G3 models. ATA drives must be configured as either a main or a slave when connecting. This is usually achieved by the use of a hardware jumper or, more than recently, through the use of a cable that can tell the drive to deed every bit either a master or slave.

ATA also goes by the name ATAPI, IDE, EIDE and PATA, which stands for Parallel ATA. ATA is still in use in many computers today, but most bulldoze manufacturers are switching over to SATA (Series ATA). If you lot have whatever devices that still use PATA drives, that's a good inkling that you're in need of an upgrade.

SATA

Equally of 2007, about new computers (Macs and PCs, laptops and desktops) use the newer SATA interface. It has a number of advantages, including longer cables, faster throughput, multidrive support through port multiplier engineering, and easier configuration. SATA drives can too exist used with eSATA hardware (discussed later) to enable fast, cheap configuration as an external drive. Most people investing in new hard bulldoze enclosures for photograph storage should exist using SATA drives.

SCSi/SAS and Fibre Aqueduct

SCSI, SAS, and Fibre Aqueduct drives are rare in desktop computers, and are typically found in expensive enterprise-level storage systems. You lot can also find SAS drives (forth with the necessary SAS controller cards) in video editing systems where maximum throughput is needed.

Some of the faster drives, such as Western Digital Raptors, come with SAS connectors, and then exist aware when you mail-guild i. Standard SATA drives can be connected to an SAS controller, only SAS drives tin't be continued to a standard SATA controller.

Hard drive enclosures

Now that we've gone over some characteristics of difficult bulldoze mechanisms, let's consider where the drive can live. The enclosure for your hard drive can exist the computer itself (for an internal bulldoze), a single-bulldoze external case, or a multiple- bulldoze external case.

Internal drives

If you are using a tower computer to shop your archive, it is likely that yous take one or more empty bulldoze bays within the estimator that tin can hold a new drive. Some advantages of using internal drives are that they are the cheapest fashion to add together storage and they take up the least amount of room. They are as well capable of connecting direct to the computer'south logic board, so they provide fast access. One drawback is that they aren't every bit like shooting fish in a barrel to swap out as external drives.

Unmarried-drive externals

Single Drive Enclosure

Figure four Adding a unmarried-drive external enclosure is an easy way to add storage to your computer system.

If you don't accept an empty bulldoze bay, or if installing a new internal drive seems as well daunting, it is unremarkably very easy to add external drives to your computer using FireWire (IEEE1394 or IEEE1394b), USB (ii or three), Thunderbolt, or eSATA connections. External single-drive cases have the advantages of beingness easily portable and not increasing the need on your reckoner's cooling arrangement. The drawbacks are the higher price and actress clutter.

You can get single-bulldoze externals in two ways.

You can purchase an external drive as a gear up-made unit. These devices offering a quick and economic way to add storage to your arrangement, merely they often come with a shorter warranty than a bare drive, and oftentimes these drives suffer from poor throughput. Manufacturers volition often sell their lowest performing drives in external cases.
Yous tin can besides purchase a freestanding enclosure and an internal bulldoze and put them together, like the i pictured in Figure four. Nosotros similar this option considering it offers more command over the components and because nosotros tin reuse the case when we outgrow the capacity of the bulldoze.

Multiple-drive externals

Multiple-drive cases are an excellent solution for a large archive. Although they are larger, at that place's less wiring clutter than with several unmarried-drive cases. And in one case you have bought a big drive box, you can fill up it with less-expensive internal drives, which y'all can later bandy out for higher capacity drives as additional infinite is required. This is the organisation that nosotros currently favor.

4 drive externals

FIGURE 5shows a four-bay external drive enclosure. This is a trayless model for SATA drives. These units provide an easy way to add more storage to your computer.

External hard drive interfaces

The hard drive mechanism has its internal interface (PATA, SATA, SAS, or Fibre Channel), and the enclosure has 1 or more external interfaces as well. The external interface determines how the bulldoze enclosure connects to the calculator. There are four principal ones in use, and a few additional ones that are used in high-terminate systems. Effigy 6 shows a drive that has the iii most mutual connectedness types.

external Hard Drive Interfaces

Figure 6 This photograph shows an external drive with all the well-nigh mutual interfaces.

USB

USB is the most universal connection method for adding peripheral devices to computers. On the PC, USB ii (stay away from USB 1 considering of its slow speeds) is a good manner to connect external drives. Information throughput maxes out at a theoretical 30 megabytes per 2d per device, in most cases. Due to the USB drivers in the Mac Os, USB is considerably slower on Apple tree machines. USB 3.0 version was recently released and offers a tenfold increase in theoretical performance. USB connectors can supply motorcoach power to attached devices.

Multiple USB devices can be connected to a unmarried port by means of an external hub.

FireWire

FireWire 400 and FireWire 800 (too known as IEEE1394 and IEE1394b) are more than modern connection protocols than USB, with theoretical transfer maximums of 50 and 100 megabytes per second. FireWire devices tin exist daisy chained, allowing the use of multiple drives on a single port. Like USB, implementations differ between Mac and PC, with Mac generally making greater use of the speed capabilities than PC. FireWire can as well offering bus power to run external drives if the FireWire port is a four-pin, six-pin or 9-pin port. (Many PCs only offer iv-pivot ports.)

Multiple devices may be connected to a single FireWire port, past ways of "daisy-chain" connectedness from ane FireWire device to some other.

eSata

eSATA is a configuration that creates a SATA connection in an external enclosure. Information technology's generally a fast and stable connexion, offer upward to 150, 300 or 600 megabytes per second. eSATA is relatively common as a built-in external connection on PC, merely is non built in to any Apple computers. You tin can add eSATA to Apple computers and older PCs by means of an expansion card, such as Peripheral Component Interface express(PCIe) for desktops and ExpressCard for some laptops.

Conventional eSATA does not have the capability to bus-power hard drives and then you must apply an external power source. We are starting to see some Powered eSATA drives on the market, just they are rare.

eSATA is often described as hot-swappable, meaning that yous can disconnect and reconnect different drives without restarting the computer, but this is ofttimes not the example. The blueprint of the host (the style the eSATA is connected to the logic board) will determine if the connection really is hot-swappable.

Multiple eSATA devices can be continued to a single port if the port supports "Port Multiplication".

Thunderbolt

In 2011, Apple released the starting time computers with a congenital-in Thunderbolt connection. This interface supports multiple streams of high-resolution video equally well equally multiple streams of fast data using the Mini DisplayPort connector. The Thunderbolt standard supports external storage devices as well as external monitors. The data connectivity of Thunderbolt is based on the same kind of PCIe connection that is used with expansion cards on tower computers – basically, it offers a direct connection to the logic board for unsurpassed speed.

The standard besides supports the employ of adapter cables that allow FireWire, USB and eSATA devices to be plugged into Thunderbolt ports. At the fourth dimension of this writing, Thunderbolt accessories, cables and peripherals are rare, probably due to the depression supply of Thunderbolt chipsets that are needed to provide the Thunderbolt connexion.

Up to vii devices (Including monitors in that count) can be connected by daisy-chain to a Thunderbolt port.

Effigy 7 The Thunderbolt connection carries both video and data over a single tiny connector.

iSCSI

Internet Small Calculator Organization Interface (iSCSI) is a connexion method that uses existing Ethernet hardware to adhere the storage to the computer. An iSCSI device can be attached directly to a computer'south network port, or a router or switch tin can connect it. It'southward fast and flexible, and offers throughput in the neighborhood of 120 MB/s.

Annotation that iSCSI needs "initiator" software that manages the connection. Some devices, such equally the DroboPro shown in Figure 8 include this software. Other iSCSI device manufacturers suggest you purchase carve up iSCSI initiator software.

Drobo iSCSI

FIGURE 8 shows the connectors on a DroboPro unit. From left to right they are USB, Firewire 800 and iSCSI.

SCSI/SAS

SAS connections tin be internal or external. This fast connection is found mostly on enterprise-level hardware, like defended servers, RAID, and tape drive mechanisms. Throughput for SAS devices is similar to SATA 2 or 3, in the neighborhood of 300 or 600 MB/due south.

Fibre Aqueduct

Fibre Channel is a engineering that has migrated from supercomputers down to enterprise-level storage (big companies). It offers a high throughput and the potential to be used over distances of several hundred feet. It can be used over copper cablevision every bit well as optical fiber. It is rated at up to 3.ii GB/south.

Choosing the right difficult drive and connection

When you add external storage to your computer, you'll desire to make certain it's fast enough for the chore at hand. Sometimes, speed won't exist terribly of import, such every bit fill-in storage for your Archive files. Sometimes speed volition exist critically important, such every bit master storage for video source files. In most cases, information technology's non hard to know when your storage speed is the workflow bottleneck. Downloads and transfers will have too long, or Photoshop volition seem to stop every bit you hear the difficult drives grinding away.

Choosing the right speed of drive and a bulldoze connection is not terribly hard, but the specifications that are published can be misleading. Sometimes, manufacturers will use the speed of a connection port as the listed speed of the device, when the actual drive is much slower than that. And many connection types don't actually live upward to the listed speed. USB 2, for case, specifies a transfer rate of 60 MB/s. Simply that'south actually for two devices on the same USB port, and there are almost no single devices that will perform faster than 30 MB/southward.

Friction match the connexion speed to the bulldoze speed

There's no point in paying a lot extra for a fast connection if the drive delivers data at a small fraction of the speed. And at that place'due south no indicate in setting upwardly fast disks and connecting them with a too-tedious connection. The chart in Effigy 9 outlines some crude data transfer rates for drive types and for connection types.

Mbps and MB/south

When you look at drive speed figures, yous will often see two different notations that look very like. Megabits per 2nd is written as Mbps, and megabytes per second is typically written as MB/s. There are eight bits per byte, so the relationship between the 2 is exactly 8:1. It'south the aforementioned with gigabits (Gb) and gigabytes (GB). When the b is lower case, the annotation is bits, when it is capitalized, it is bytes. Since most of us think in bytes rather than bits, that'southward the one we'll use for comparison.

For instance, FireWire 400 is named for the number of megabits that tin exist transferred in a 2nd, which is nearly 400. Divide that by 8 to get the number of megabytes that can be transferred in a 2d: 50. (Information technology's actually just a little chip less: 393 Mbps and 49 MB/s).

Of course, a gigabyte is k megabytes, and then once measurements get higher up 1000 MB/s, we change to GB/south.

Note that there is a difference between the rated speed and the typical real-world speed. All connections provide slower actual throughput than the rated speeds – some significantly so. Check the chart in Figure 9 to get a meliorate idea of actual speed.

Difficult drives well-nigh never achieve maximum throughput

It'southward very hard to outline existent-world speed for a drive. Hard drives are slowed down considerably when they read or write small files. Information on the outer rings of a drive platter is read faster than information on the inner rings. And as a drive fills up, things slow down even more.

A unmarried 7200 RPM drive, for instance, should outperform a FireWire 800 connection, since peak data transfer is typically above FireWire 800'southward 98 MB/s. But you will only find that happening in rare circumstances – in most cases, the drive will be serving up data at a significantly slower rate.

Bigger files transfer much faster than smaller files

When you transfer a big file, your drive tin can spend most of its time actually reading or writing data, so it works at its well-nigh efficient pace. When you transfer smaller files, the drive spends a lot more than fourth dimension "seeking" the files – moving the head to the role of the data platter that contains the files.

SSDs are able to do a much better job with small files, since no parts demand to move to the place the data is stored, simply smaller files nonetheless ho-hum SSDs down. That's considering there'southward a certain amount of authoritative overhead associated with each file read or write.

Bigger drives are normally faster

There are several reasons that larger capacity drives are ordinarily faster than a comparable RPM drive of smaller capacity.

Most of import, the larger drives are probably newer and, like most calculator components, newer is going to exist faster due to general technological development.
Bigger drives are besides more dense, which means the head has to travel a shorter distance between data $.25. This speeds up the throughput.
Bigger drives will have less data fragmentation, since there is more than room to write files contiguously. This results in reduced seek time.

Bulldoze and connection speed chart

The following chart lists sample speeds for hard drive devices. It tin can help you decide which external bulldoze connection is correct for you lot. Note that it's only a crude guide. It is based on the full general speeds of new difficult drives of good brand-name quality.

Utilize this chart to help determine which parts of your storage configuration may be slowing you down. You can also use it to make certain that any new storage devices you buy volition match the throughput of the connexion type. (For instance, a high performance SSD would be wasted if it is on a slow FireWire 400 connection).

Figure 9 This chart shows the connection speed of storage devices, connections types and network configurations, as measured in megabytes per second. These are typical speeds for maximum throughput when transferring big files. Pocket-sized file transfer will exist significantly slower, especially for conventional hard drives.

Difficult drive ability supplies

Which power supply the drive will use depends on the example blueprint. An internal drive added to a belfry reckoner volition use the reckoner's power supply. This is tidier because you don't accept ability cables running all over the place. It does tax the calculator's ability supply, however, and that can atomic number 82 to failure.

The power supply for unmarried-bulldoze external cases is typically a ability brick that sits outside of the case. If you are going to employ these, try always to buy the aforementioned brand and then that yous accept swappable components to test if there is a problem.

The power supply for a multiple-bulldoze enclosure is commonly inside the example, and is a lot like the power supply inside your reckoner. If it fails, you can transfer the drives into another enclosure and keep working. (If the drives are in a RAID configuration, you'll only desire to transfer them to an exclosure with an identical RAID controller.)

Double-decker-powered drives

Portable drives with two.five-inch disks within often use the power in USB or FireWire cables to provide electricity to the drive. This is a real convenience for portable devices, just there are a few caveats. Some drives (particularly faster ones) require more current than is supplied past the port. In these cases, the drive will either not fully mount or might disappear when the ability draw gets likewise big. Unfortunately, the merely way to see if a drive works with your figurer is to hook it upwardly and give it a try.

There's another note of caution that you should be enlightened of when using jitney-powered drives. As well loftier a current draw can burn out the port that the drive is connected to. This seems to be typically associated with running multiple drives daisy chained off a laptop'southward FireWire port. If y'all need to run more than ane drive off a single port, you should buy 1 that volition have an external power adapter.

SMART status

Cocky-Monitoring Analysis and Reporting Technology (SMART) keeps track of status and error information for a drive and tin can be helpful in predicting drive failure. Almost current computers can give you a pass/fail SMART status for internal drives, every bit well every bit for some eSATA-connected drives (if the eSATA port volition support SMART data). Yous can besides access the raw values, if yous would like a more than nuanced report on how well the drive is doing.

SMART information is not available for drives connected by FireWire or USB.

READ More IN THE Data VALIDATION Section

FIGURE 8SMART Utility is a program that can read the raw SMART values from a drive and give y'all specific information nearly its condition.

Difficult drive volume configurations

Now that we know almost drives and how they tin can physically be connected, nosotros demand to know nearly the logical configuration. Does each bulldoze prove up as a single volume, as multiple volume partitions, or do multiple drives bear witness up as though they were a unmarried bulldoze?