The fast, reliable, economical external SATA.
Protecting your data can be as simple as saving crucial files to a USB flash stick, to burning a CD or an internal drive RAID configuration. One other popular method for desktop data protection is USB or Firewire (1394) interfaces for 2.5 or 3.5-inch external disk drives. There are just as many methods if not more to back up corporate or business data such as, near-line, bulk storage, JBOD, and NAS storage. For off-line or archival data there is tape drive back up. Although there is a place for eSATA in the Near-line and Off-line segment this article will focus mainly on eSATA usage with PCs, Servers, Workstations and even Notebook data protection.
In addition, eSATA can provide the fastest external DV editing crunch power combined with terabytes of ATA storage all at very low price. eSATA's speed and flexibility bring a new breed of external storage and new expectations for high performance external solutions. The application possibilities of eSATA solutions are endless.
eSATA is not as simple as moving a SATA port to the back of the PC however. SATA internal cables and connectors would not be adequate for "out-side the box" or outside the PC usage. The following concerns needed to be addressed before SATA could be extended safely outside the box and be approved by the Serial ATA International Organization (SATA-IO):
* Preventing Electrical Static Discharge (ESD) damage during insertion
* Electro Magnetic Interference that met the FCC and CE emissions requirements
* Robust cable and connection assemblies for multi-insertions vs. one time installation of internal storage
* Prevention of unshielded connections in external connectors
To resolve these concerns the new eSATA specification was authored by SATA-IO member companies and those members, who build solutions that adhere to the specification. Early external SATA solutions may not meet the requirements of the eSATA specification. Make sure you look for the eSATA logo for a product that adheres the latest Serial ATA specification.
eSATA is merely SATA out side the box but with more robust cables and connections. eSATA can operate at the same speeds as internal SATA, such as SATA 1.5Gb/s (150 Mbytes/sec) or SATA 3Gb/s (300 Mbytes/sec). eSATA 3Gb/s speed is backward compatible to 1.5Gb/s just like internal drives are today. With drive internal sustainable data rates reaching as high as 75Mbytes/sec the interface rates of USB and 1394 will soon become the bottleneck for disk drive based external drives. In addition, eSATA enables external storage to utilize features and mechanisms such as Native Command Queuing, Hot Plug, Port Multipliers and many more advanced SATA features.
eSATA Opens Doors to Higher External Performance
eSATA, as a single drive solution with a high data rate can provide an end-user with blazing fast external data transfer rates like they've never had before from an external back up solution. But the power of eSATA can be unleashed with features and mechanisms such as: SATA 3Gb/s PCI HBAs, RAID and Port Multipliers. Single external drives can be aggregated as one large external drive with an interface rate up to 300MB/s or these same drives can be integrated as a RAID 0, 1, 5 or even 3 to provide continuous data protection with absolutely no end-user interaction. You'll never have to ask your client again if he backed up because his/her system was designed to continuously backup data without a single touch.
Better Desktop Backup
Backing up to CDs is cheap and easy but it still requires the user to remember to do it. If the system is lost between backups, the data is gone. eSATA can be designed to constantly provide data redundancy through a mirror RAID or through parity protection of two or three drives. The host solution is key. You should choose an HBA that supports the type of features you need from simple RAID 0 to advanced RAID 5. To find solutions today visit the SATAIO industry organization membership list.
When combining a few single eSATA disk drives with a Port Multiplier the throughput results reach well over 200Mbytes/sec. These results are courtesy of Silicon Image. Notice that 1394b is limited to ~61MB/sec due to the overhead of the interface of approximately 20Mbytes/sec. This is actual throughput of a two drive RAID 0 setup using a Silicon Image eSATA controller and eSATA disk drives vs. 1394b external storage. As you can see, eSATA easily doubles the performance of the next fastest external interface 1394b in a RAID 0. Today's highest areal density for a single disk drive is 120Gbsi equating to ~75Mbytes/sec throughput--that alone exceeds the interface limitations of 1394b, formerly the industry's fastest external interface.
eSATA Flexibility from Desktop to Enterprise
eSATA solutions can be designed in as a single drive back up solution or a higher end "no down time" back up and restore solution. The disk drives themselves can be single units within individual enclosures or multi-drive enclosures with two or more hot-plug drives with a single eSATA cable connecting devices to the host controller. How advanced your solution becomes depends on your host solution. Motherboards with a single eSATA connection coming out the back of the PC, along side USB and/or 1394b ports, are available today from at least two different motherboard manufacturers. PCI and PCI-X HBA solutions are also available and the power combined with user friendliness of these solutions enable them to be perfect solutions for that accident-prone end-user who needs "no complications" data protection. But in addition, eSATA is a very fast, redundant backup and restore solution for IT usage. Imagine the ability to quickly increase server storage by 500 Gbytes in a small to medium business in a matter of minutes. The system design would be an eSATA enclosure attached to the server using SATA hot plug drives. When the storage becomes close to saturation, the IT engineer pulls out a smaller drive and upgrades to a new 500GB drive without ever bringing down the system. The host controller may contain it's own processor that allows the real build without any Server CPU utilization. Or the Server motherboard can integrate two or more eSATA ports and the upgrade could be as simple as plugging in another eSATA drive or enclosure and your capacity is almost limitless. Most back up and restore solutions do not solve downtime problems but eSATA can if it's designed in with the right host solution.
The ATA Cost Advantage
You've read that eSATA is faster than USB and 1394b--double in some cases but how does it compare to higher end solutions such as SCSI and SAS? The difference at this point becomes more drive hardware related. For instance, most SCSI drives are 10K or even 15K spindle speeds which provide higher mechanical performance. These drives are also designed to work in extreme temperatures under the harshest environments such as high shock and vibration--all the while maintaining performance and reliability levels. This type of robust performance doesn't come cheap. But if this doesn't sound like your workload, you can take advantage of the new breed of low cost, high capacity SATA and eSATA storage. eSATA can be as large as today's largest SATA drives. 500GB in a single drive enclosure or with multi-drive enclosures eSATA can easily reach 1.5 Tbytes with just three drives. The possibilities seem endless.
eSATA technology will not be the answer for all back up or even all data protection needs but for those who want reliable, economical and user friendly external storage eSATA may be the best choice for your needs.
Joni Clark is Serial ATA product marketing manager at Seagate Technology, Scotts Valley, CA
Figure 1. 1394b vs eSATA: RAID 0 Sequential Read Test (IOMeter) MB/Sec Block Size eSATA 1394b 256k 113.6 81.2 128k 113.5 81.9 64k 113.5 62.2 32k 99.5 51.3 16k 73.1 37.0 8k 52.8 24.1 4k 35.2 13.7 2k 22.2 6.9 1k 11.3 3.4 Note: Table made from line graph.
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|Title Annotation:||Connectivity; Serial Advanced Technology Attachment (hard disk interface)|
|Publication:||Computer Technology Review|
|Date:||Aug 1, 2005|
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