TweetFollow Us on Twitter

Storage Interconnect Technologies

Volume Number: 21 (2005)
Issue Number: 9
Column Tag: Programming

Media Exchange: Storage Interconnect Technologies

A Quick Reference and Guide to IDE/ATA, SATA, eSATA, SCSI, SAS, Fibre, IEEE 1394, USB and RAID Technologies

by Emmanuel Stein

Introduction

With all of the exisiting storage interfaces to choose from, Mac professionals are routinely faced with a bewildering array of technology and configuration options. Moreover, with Apple's entrance into the high-end enterprise server market, the identification and implementation of the array of extant interconnect technologies has become an increasingly complex task. This article represents a compass for Mac professionals to navigate the maze of available solutions. Using a modified glossary-style format, each technology is defined in detail with practical commentary on the application of the various technologies covered. Whenever appropriate, I reference how these technologies apply to the Mac and give readers a sense of what technologies are being developed and which ones will likely be supplanted in the near term.

Parallel ATA (IDE/ATA)

Advanced Technology Attachment (ATA) is a parallel interface for connecting internal storage devices to personal computers and has many aliases including ATA/ATAPI, EIDE, ATA-2, Fast ATA, ATA-3, Ultra ATA, and Ultra DMA. ATA supports two devices per bus with only one drive able to access said bus at a time. ATA-7 (ATA-133), the current and final revision of the ATA specification, supports a maximum data transfer rate of 133 MBytes/sec across an 18-inch cable. Although ATA is best suited to low cost consumer storage solutions, it has been successfully adapted to the enterprise market, via clever hardware engineering on Apple's part in their Xserve RAID product, which overcomes many of the shortcomings of ATA. Every ATA drive in the Xserve RAID is connected to a dedicated bus, with two independent and non-redundant controllers that support non-native Tagged Command Queuing, an essential feature for enterprise-grade storage solutions. PATA is, nevertheless, a technology of the past and, though it is still employed in low end Macs and other devices, it is being replaced by its serial counterpart.

Serial ATA (SATA)

SATA is quickly replacing parallel ATA as the internal storage interface of choice for desktop machines and low cost server solutions. SATA made its Mac debut in Apple's PowerMac G5 line and has been extended the new iMac line. SATA has also been used in newer Xserves, with the notable exception of the Xserve RAID. SATA remains compatible, on the software level, with ATA and, therefore, all the existing firmware, operating systems, and applications that work with ATA will also work with SATA. SATA advantages include point-to-point interconnect that enables full bandwidth for each drive, native command queuing, lower voltage requirements, hot-plug capability, thin cabling, longer cable length, faster transfer rate and CRC error checking. These added features make SATA suitable for cost sensitive server deployments.

    SATA - maximum transfer rate is 150MBytes/sec over a cable up to 1 meter long

    SATA II - maximum transfer rate is 300MBytes/sec over a cable up to 1 meter long

    SATA-III - maximum transfer rate is 600MBytes/sec (will be available in 2007)

External SATA (eSATA)

ESATA is an emerging external storage interface extension to SATA, which offers an inexpensive and faster external storage solution and is poised to overtake FireWire disk implementations, so common in the today's Mac environments. Currently, eSATA supports a maximum transfer rate of 150MBytes /sec and has a maximum cable length of 2 meters.

Parallel Small Computer System Interface (SCSI)

Parallel SCSI, better known as just plain SCSI, is a parallel bus technology that connects a variety of peripherals to one's computer. Parallel SCSI can support up to 16 devices on a single bus. Although it offers faster throughput and comes with more advanced drive features than ATA, its price to performance ratio leaves something to be desired. SCSI's parallel nature makes it hard to deploy in larger environments and the technology has reached its practical performance limit. Ultra 320 is the last line in the evolution of parallel SCSI and supports a maximum transfer rate of 320MBytes/sec over a cable up to 12 meters in length. Although SCSI has dominated the enterprise market for the past two decades, SAS represents a natural evolution of the technology, which is likely to eclipse SCSI in the near term.

Serial Attached SCSI (SAS)

SAS is a serial implementation of SCSI that is designed to extend the existing capabilities of parallel SCSI and enables compatibility with Serial ATA. SAS allows users to interconnect either SATA or SAS hard disks within an expander that can be configured to support up to 16,256 mixed drives An essential component of the SAS infrastructure, expanders enable scalable storage with extended distances between devices and support for multiple device attachment to multiple host initiators, thereby affording fault tolerance. The maximum cable length of SAS is 10 meters. SAS also supports smaller storage devices such as 2.5-inch drives. Its point-to-point configuration and highly scalable architecture makes SAS an advanced, high-cost enterprise-class solution for applications that do not require the long cable lengths associated with Fibre technologies.

    SAS 300 - maximum transfer rate is 300MBytes/sec

    SAS 600 - maximum transfer rate is 600MBytes/sec (will be available in 2007)

    SAS 1200 - maximum transfer rate is 1200MBytes/sec (will be available in 2010)

Fibre Channel (FC)

Fibre Channel is a serial bus interface for high-speed storage solutions. It is interoperable with SCSI, IP, ATM, HIPPI and IEEE 802.2 protocols and offers a maximum data transfer rate of 400 MBytes/sec, with a maximum length of 30 meters over copper and 10 kilometers using optical. Fibre Channel offers point-to-point, switched, and loop interfaces. Via arbitrated loop (FC-AL), fibre channel can support up to 127 devices and up to 15,663,104 using switched fabric. Fibre has been increasingly deployed for enterprise applications such as SAN (Storage Area Network), which benefit from Fibre Channel-specific features like long cable length and capacious device support.

FireWire/IEEE-1394/i.Link

FireWire is a high-speed serial bus developed by Apple. It offers simple connectivity for multimedia peripherals such as digital video cameras, iPods and high-performance storage. FireWire can connect up to 63 devices on a single bus and supports hot-swapping. FireWire was originally designed for streaming digital video and, therefore, was not implemented with heavy file serving in mind, with its frequent random reads and writes. FireWire hard drives have been widely deployed as an inexpensive backup solution, particularly in Mac environments. Although cable length is limited to 4.5 meters, distances up to 50 meters can be achieved using plastic optical fibre (POF) and 100 meters with hard polymer or glass-based fiber cabling. Although, not considered an enterprise grade solution, Apple's popularization and support for this technology, have gone a long way to legitimizing its use in the enterprise, as well as, home environments.

    FireWire 400 - maximum transfer rate is 400 MBits/sec

    FireWire 800 - maximum transfer rate is 800 MBits/sec

Universal Serial Bus (USB)

USB is designed for a variety of peripheral interconnect applications. A single USB channel can connect up to 127 devices with a maximum cable length of 5 meters. External USB-based hard drives are popular among PC users since FireWire does not typically come standard. Although used in many third party storage solutions, USB-based hard drives not appropriate for server or other high-end applications like digital video and file serving.

    USB 1.1 - maximum transfer rate is 12 MBits/sec

    USB 2.0 (Hi-speed USB) - maximum transfer rate is 480 MBits/sec

Redundant Array of Independent Disks (RAID)

RAID is a method of consolidating multiple drives into Logical Units (LUNs). RAID can be implemented using extant hard drive technologies, including SCSI, SATA, and ATA. Depending on the particular RAID configuration used, benefits will include increased data integrity and redundancy, facilitated disk cluster management, fault-tolerance, and improved throughput. RAID solutions are commonly used in the enterprise and have now gained a foothold in the high-end consumer market.

    RAID 0 - also known as striping, splits data evenly across all drives and lacks parity information for redundancy. It increases performance in read and write operations, but introduces an increased rate of failure with each disk added. RAID 0 is recommended for applications that are not data critical but require high speed such as audio and video streaming and editing, graphic design and high-end gaming systems.

    RAID 1 - aka mirroring creates an exact copy of the data on two or more disks. It increases performance in read operations but imposes a small penalty for write operations. RAID 1's inefficient use of the disk space is considered its main drawback. It is well suited, however, to data critical applications in which superior reliability is required.

    RAID 0+1 - a combination of RAID 0 and RAID 1, a mirror of stripes. Benefits include increased performance in read and write operations while maintaining data redundancy. Disadvantages include high cost and limited scalability. Performance is severely degraded during recovery, since all disks in an array must participate in the rebuilding process. RAID 0+1 is recommended for imaging applications and general fileserver tasks that require high performance but do not demand maximum redundancy,

    RAID 3 - byte-level striping with a dedicated parity disk. Its random read/write performance is poor due to byte-level striping, parity calculation overhead and the bottleneck of a dedicated parity drive. RAID 3 is useful for applications that deal with large files such as video editing and prepress, which benefit from increased performance with redundancy.

    RAID 5 - data and parity information are striped across all drives. It is the most popular of the RAID configurations because it provides a good balance between availability, capacity, data protection and performance relative to other RAID implementations. RAID 5 is often employed in transaction processing applications such as web, e-mail, and news servers, where large numbers of users access information concurrently.

    RAID 10 - a combination of RAID 1 and RAID 0, a stripe of mirrors. It is very costly to deploy and suffers from limited scalability. Unique advantages include rapid data transfer, with its striped array, and superior data redundancy. RAID 10 is used in database solutions that require high performance and fault tolerance.

    RAID 50 - block striping with the distributed parity of RAID 5 combined with the block striping of RAID 0. This combination achieves fast transfer rates via distributed parity and is very costly to implement. RAID 50 is only recommended for data critical applications that require high fault tolerance with fast read/write operations.


Emmanuel Stein has been an avid Mac user since 1984 and has honed his cross-platform skills while working at France Telecom, Time Magazine and Reed-Elsevier. He has recently started his own Mac-centric consulting company, MacVerse, which offers implementation, system administration and development services geared towards the enterprise market. As a diehard GNU/Linux geek, he enjoys hacking open source software and experimenting with new open source projects on OS X. You may reach him at macverse@mac.com


What's the best direction?

Now that you have a better idea as to what all the different technologies are with their strengths and weaknesses, which do you use? Unfortunately, there is no one easy answer, but we thought we'd give you one example of a way to take advantage of these technologies.

Here at MacTech Magazine, we're always bringing in new equipment and replacing old stuff. It's part of the magazine process. Recently, we decommissioned an older Power Mac G4 tower machine, which was running perfectly fine, and was wondering what to do with it. As a 450MHz G4, it wasn't fast enough to be a workstation, but it was plenty fast to be aserver ... depending on the type.

We chose to turn it into another file server. We installed Mac OS X Server on it, gave it 768MB of RAM, and then started to look and see what disks we could put into it. The problem with the older machines is that they, many times, don't support drives larger than 128GB, and we weren't going to invest in drives that small.

Instead of investing in old technology, we decided to combine the best of new and old. In this case, we went with SATA drives from Maxtor. Why SATA? Well, for starters, they break the 128GB barrier as a general rule.

And, these Maxtor drives are designed to live for a minimum of 5 years. Meaning that even though these are going in an older machine, we're investing in technology that will be useful for a while. We can use these drives for something else down the road. This is one of the best reasons to go with SATA instead of Ultra ATA.

Specifically, we went with the Maxtor DiamondMax 10. These Serial ATA drives feature a 16MB buffer, at 7200 RPM, and a data transfer rate of 150 MBps. At time of writing, street prices are between $110 and $160 for these drives making them a cost effective solution.

But my machine doesn't support SATA!

Yep, none of the older ones do. No worries. You can get an inexpensive SATA PCI card for around $50. In our case, we used one from Sonnet, and attached two SATA drives to the one cord. Don't forget, both the interface cables and the power cables are different than ATA. You'll need a power adapter cable, and SATA interface cables if they don't come with your card.

What else is cool out there?

Maxtor has some other cool stuff as well. The Maxtor Shared Storage drive is a budget conscious way to share files. It's basically, a low cost file server that you attach to your network, is automatically configured (and can be further configured in a web interface) and can even help you share two USB printers. They come in 200 and 300 GB versions.

Maxtor also has some great "OneTouch" devices which you can use as either an external drive, or as an easy way to do a "one touch" backup. The Maxtor OneTouch II, FireWire 800 Edition actually sports a triple interface: FireWire 800, FireWire 400 and USB 2.0. Its Mac bootable feature turns a drive into a bootable system drive. It includes a simple user interface and automated back-up software so you can designate a portion of drive for high-performance storage and the other portion for backing up critical data. Two capacities: 200 GB (MSRP: $229.95); 300 GB(MSRP: $319.95)


by Neil Ticktin, publisher of MacTech Magazine.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Adobe Illustrator 24.0.3 - Professional...
You can download Adobe Illustrator for Mac as a part of Creative Cloud for only $20.99/month (or $9.99/month if you have also purchased an earlier software version). Adobe Illustrator for Mac is the... Read more
Adobe Dreamweaver CC 2020 20.1 - Build w...
Dreamweaver CC 2020 is available as part of Adobe Creative Cloud for as little as $20.99/month (or $9.99/month if you're a previous Dreamweaver customer). Adobe Dreamweaver CC 2020 allows you to... Read more
Adobe Audition 13.0.3 - Professional pos...
Audition is available as part of Adobe Creative Cloud for as little as $20.99/month (or $9.99/month if you're a previous Audition customer). Adobe Audition empowers you to create and deliver... Read more
Adobe After Effects 17.0.3 - Create prof...
After Effects is available as part of Adobe Creative Cloud for $52.99/month (or $20.99/month for a single app license). The new, more connected After Effects can make the impossible possible. Get... Read more
Audio Hijack 3.6.4 - Record and enhance...
Audio Hijack (was Audio Hijack Pro) drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio... Read more
Eye Candy 7.2.3.96 - 30 professional Pho...
Eye Candy renders realistic effects that are difficult or impossible to achieve in Photoshop alone, such as Fire, Chrome, and the new Lightning. Effects like Animal Fur, Smoke, and Reptile Skin are... Read more
Notability 4.2.2 - Note-taking and annot...
Notability is a powerful note-taker to annotate documents, sketch ideas, record lectures, take notes and more. It combines, typing, handwriting, audio recording, and photos so you can create notes... Read more
Adobe Acrobat Reader 20.006.20034 - View...
Adobe Acrobat Reader allows users to view PDF documents. You may not know what a PDF file is, but you've probably come across one at some point. PDF files are used by companies and even the IRS to... Read more
Adobe Acrobat DC 20.006.20034 - Powerful...
Acrobat DC is available only as a part of Adobe Creative Cloud, and can only be installed and/or updated through Adobe's Creative Cloud app. Adobe Acrobat DC with Adobe Document Cloud services is... Read more
Day One 4.8 - Maintain a daily journal.
Day One is an easy, great-looking way to use a journal / diary / text-logging application. Day One is well designed and extremely focused to encourage you to write more through quick Menu Bar entry,... Read more

Latest Forum Discussions

See All

Marvel Strike Force introduces new brawl...
FoxNext's squad-based RPG Marvel Strike Force is set to receive some fresh characters from the X-Men and Iron Man series. They'll arrive as part of the game's latest update, which follows a sizable spending boycott on the title due to complaints... | Read more »
Speed Dating for Ghosts is a narrative a...
Speed Dating for Ghosts originally released on Steam back 2018, since then it has received honourable mentions for narrative during the Independent Games Festival. Now it's made its way over to iOS devices where it's available as a premium title... | Read more »
Fast-paced multiplayer title Tennis Star...
Tennis Stars: Ultimate Clash is the latest free-to-play tennis title to hit iOS and Android. It's said to be a fairly casual experience, offering easy-to-learn controls and fast-paced, mobile-friendly matches. [Read more] | Read more »
Super Mecha Champions' latest updat...
Super Mecha Champions' latest update sees the addition of a brand new character called R.E.D. Alongside that, there's news about the current season and a series of Emojis that have been added to the game. [Read more] | Read more »
Isle Escape: The House is an upcoming pu...
Isle Escape: The House is an upcoming puzzle game from Simeon Angelov that's intended to serve as an introduction to a saga they're planning on releasing in an episodic fashion. The first chapter is set to release for both iOS and Android on 29th... | Read more »
Company of Heroes, the classic RTS, is n...
Feral Interactive has finally released their highly anticipated iOS version of the strategy classic Company of Heroes. It's available now for iPad as a premium title and has had various tweaks to ensure that it's optimised for touch controls. [... | Read more »
Mario Kart Tour's Vancouver Tour ha...
With Mario Kart Tour's Valentine's Tour now at an end (suspiciously before Valentine's Day has even arrived), it's now time to move on to the all-new and exciting Vancouver Tour. This time around, the featured drivers are Hiker Wario and Aurora... | Read more »
A new PictoQuest update makes it a much...
PictoQuest is a charming little puzzle game, but it left us a little disappointed. The game just didn’t seem to use screen space effectively, to the point that using the touch controls (as opposed to the default virtual d-pad) could lead to errant... | Read more »
Alley is an atmospheric adventure game a...
Alley is an atmospheric adventure game that sees you playing as a young girl trapped in an inescapable nightmare. Surrounded by her worst fears, every step forward for her is a huge challenge that you'll help guide her through using some simple... | Read more »
Fight monsters and collect heroes in Cry...
From Final Fantasy to Chaos Rings, Japanese roleplaying games have found a large and loyal fanbase on mobile devices. If you’re seeking a more under-the-radar JRPG to escape into, Lionsfilm’s Cryptract could be the one. The game has been around... | Read more »

Price Scanner via MacPrices.net

Apple AirPods are on sale for $30 off today
Amazon has new 2019 Apple AirPods (non-Pro models) on sale today for $30 off MSRP, starting at $129. Shipping is free: – AirPods with Wireless Charging Case: $169 $30 off MSRP – AirPods with Charging... Read more
27″ 3.7GHz 6-Core 5K iMac on sale for $2099,...
B&H Photo has the 2019 27″ 3.7GHz 6-Core 5K iMac in stock today and on sale for $200 off Apple’s MSRP. Overnight shipping is free to many locations in the US: – 27″ 3.7GHz 6-Core 5K iMac: $2099 $... Read more
Save up to $250 on a 12.9″ iPad Pros with the...
Apple has Certified Refurbished 12.9″ iPad Pros available on their online store for up to $250 off the cost of new models. Prices start at $849. Each iPad comes with a standard Apple one-year... Read more
Save up to $220 on 11″ iPad Pros with these r...
Apple has Certified Refurbished 11″ iPad Pros available on their online store for up to $220 off the cost of new models. Prices start at $679. Each iPad comes with a standard Apple one-year warranty... Read more
8-Core 27″ iMac Pro available for $4249, Cert...
Apple has Certified Refurbished 27″ 3.2GHz 8-Core iMac Pros available for $4249 including free shipping. Their price is $750 off the cost of new models. A standard Apple one-year warranty is included... Read more
$749 MacBook Airs continue to be available on...
Amazon has the 2017 13″ 1.8GHz/128GB MacBook Air on sale today for only $749 shipped. That’s $250 off Apple’s original MSRP for this model and the cheapest new MacBook available from any Apple... Read more
HomePods on sale for $204 at Other World Comp...
Other World Computing has discounted, new, Apple HomePods on sale for up to $95 off Apple’s MSRP: – HomePod Space Gray: $207.99 $92 off MSRP – HomePod White: $204.99 $95 off MSRP These are the same... Read more
Get a Certified Refurbished iMac at Apple for...
Apple has Certified Refurbished 2019 21″ & 27″ iMacs available starting at $929 and up to $350 off the cost of new models. Apple’s one-year warranty is standard, shipping is free, and each iMac... Read more
A Look Back At The Top 5 Most Read Stories Of...
FEATURE: 02.21.20 The best of the best are now history and we’re not talking about Super Bowl LIV from earlier this month but rather, coverage from the past year (its second and first full one at... Read more
Apple offers wide range of discounted custom...
Save up to $610 on a custom-configured 21″ or 27″ iMac with these Certified Refurbished models available at Apple. Each iMac features a new outer case, free shipping, and includes Apple’s standard 1-... Read more

Jobs Board

Medical Assistant - *Apple* Valley Clinic -...
…professional, quality care to patients in the ambulatory setting at the M Health Fairview Apple Valley Clinic, located in Apple Valley, MN. Join the **M Health Read more
Geek Squad *Apple* Consultation Professiona...
**756636BR** **Job Title:** Geek Squad Apple Consultation Professional **Job Category:** Store Associates **Store NUmber or Department:** 001053-Arundel Mills-Store Read more
Medical Assistant - *Apple* Valley Clinic -...
…professional, quality care to patients in the ambulatory setting at the M Health Fairview Apple Valley Clinic, located in Apple Valley, MN. Join the **M Health Read more
*Apple* Certified Repair Technician - Utah S...
…selected candidate will work in the USU Campus Store Tech Department as an Apple Certified Repair Technician and floor associate. This position is for both summer Read more
*Apple* Mobility Pro - Best Buy (United Stat...
**744429BR** **Job Title:** Apple Mobility Pro **Job Category:** Store Associates **Store NUmber or Department:** 000574-Garner-Store **Job Description:** At Best Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.