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SAS Performance at SATA Pricing: Cost-Effective SAS RAID Controller

SAS that was reserved more for the enterprise or server market. It is no longer the case with the release of cheaper SAS controller expansion card. Today, we will be comparing 15,000 RPM SAS drives in RAID 0 with 7,200 RPM SATA drives in RAID 0 to see the performance difference between the two configurations. Read more and see if it would be worth to upgrade to the 15,000 RPM SAS drives if you want the best performance.

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INTRODUCTION

What is important when shopping for hard drives is the storage space, rotational speed, amount of cache, and of course the price. Currently, for desktop computers, 7,200 RPM SATA II hard drives are the most common type of storage. For enterprise and business, there is SAS, which stands for Serial Attached SCSI.

Although SAS HDD’s are primarly aimed for the enterprise market whose main goal is to achieve the highest performance, the fact that you can find these drives in speeds of up to 15,000 RPM makes them a good candidate for enthusiasts as well. Current desktop SATA HDD’s have rotational speed of either 5,400 rpm or 7,200 rpm. For the enthusiasts, SATA drives can be found in speeds up to 10,000 RPM. SAS, on the other hand, can be found commonly at rotational speed of 10,000 RPM and 15,000 RPM.

What determines the performance of any hard drive is the rotational speed, the amount of cache, and the lesser known information, the platter density.  Generally speaking, when shopping for a high performance hard drive, one should look for the highest density per platter (with 320GB/platter being the highest at the moment) and fastest rotational speed. Thus, at 15,000 RPM, SAS hard drives are the performance leader of conventional HDD’s and should prove to have the best performance.

Although, Solid State Drives are the talk of the industry for being the replacement of conventional spinning platter disks, the truth is that current Solid State Drives are insanely expensive, the storage capacity is pale compare to the terabytes offered by the SATA, and the write speed is yet to perform on par with mechanical drives. Thus, we are not going to see them to become widely available any time soon, but with technology improvements, we should see them becoming more accessible to enthusiasts and even hitting the mainstream market.

This is where SAS drives come in. Although SAS drives are relatively expensive compared to SATA drives, they are not as expensive as SSD’s and are able to offer better performance than SATA with more balanced read and write performance than SSD’s. Today, we will be comparing the 15,000 RPM SAS drives running in RAID 0 versus 7,200 RPM SATA drives in RAID 0 to see the performance gains of going with the SAS drives.

SAS

 

Physically, looking at the connectors for SAS and SATA, it is not that hard to tell them apart. SAS has a continuous connector for both data and power while SATA has a separate data and power connector. Although the SAS controller will be able accommodate SATA hard drives, SATA controller does not support SAS hard drives.

Current theoretical transfer speed of both SATA and SAS is 300 MB/s. Faster transfer speed is in the works with 600MB/s as the theoretical transfer speed, which may appear as early as 2009. One area where SAS hard drives have advantage over SATA hard drives is the rotational speed. Currently, the maximum rotational speed for SATA hard drive tops out at 10,000 RPM while 15,000 RPM SAS hard drives can be found easily on the market.

Despite the fact that both SAS and SATA use serial protocol for data transfer, SAS can be considered as more advanced version of SATA. Here are some differences between SAS and SATA from Wikipedia:

  • Most SAS drives provide Tagged Command Queuing, while most newer SATA drives provide Native Command Queuing, each of which has its pros and cons.
  • SATA follows the ATA command set and thus only supports hard drives and CD/DVD drives. In theory, SAS also supports numerous other devices including scanners and printers. However, this advantage could also be moot, as most such devices have also found alternative paths via such buses as USB, IEEE 1394 (FireWire), and Ethernet.
  • SAS hardware allows multipath I/O to devices while SATA (prior to SATA II) does not. Per specification, SATA II makes use of port multipliers to achieve port expansion. Some port multiplier manufacturers have implemented multipath I/O leveraging port multiplier hardware.
  • SATA is marketed as a general-purpose successor to Parallel ATA and is now common in the consumer market, while the more expensive SAS is marketed for critical server applications.
  • SAS error recovery and reporting utilize SCSI commands which have more functionality than the ATA SMART commands used by SATA drives.
  • SAS uses higher signaling voltages (800-1600 mV TX, 275-1600 mV RX) than SATA (400-600 mV TX, 325-600 mV RX). When SAS is mixed with SATA, the SAS drives run at SATA-voltages. One reason for this higher voltage is so SAS may be used in server backplanes.
  • Because of its higher signaling voltages, SAS can use cables up to 8 m (25 ft) long, SATA is limited to 1 m (3 ft).

Source: Wikipedia

PRICE VS PERFORMANCE

Many users probably will be wondering if it would be worth it to upgrade to a SAS drives given to the cheap price of SATA hard drives. However, to get the best performance, sometimes price really is not going to be a factor. In fact, if you consider the price for the Western Digital’s 300GB VelociRaptor which sells at $270.99, and Fujitsu’s MBA3300RC 300 GB which can be purchased at retail price of $380; the difference in the price may not seem as big as when it is compared to the 7,200 RPM SATA drives.

Feature/Specification

 500 GB 7,200 RPM SATA

 300 GB 10,000 RPM SATA

300 GB 15,000 RPM SAS
Price per single drive
$99.21
$270.99
$380.00
Number of Drives(RAID  0)
2
2
2
Controller
$0 onboard
$149.99 add-on
$0 onboard
$149.99 add-on
$149.99 add-on
Total Cost for RAID 0 
$198.42 onboard
$348.41 add-on
$541.998 onboard
$691.97 add-on
$909.99 add-on

There is additional cost must be considered when upgrading to SAS drives and that is the need for an external add-on card. SAS is usually reserved for server boards and none of the current desktop motherboards have a SAS controller, thus, an add-on card is a must. Luckily there are various vendors for such controllers and the price for them is not too expensive for a budget card that support RAID 0/1/5/10 JBOD.

We have received HighPoint Technologies RocketRAID 2640×4 for the review. This card is one of the cheapest PCI-Express based SAS controllers. Selling at retail price of $149.99 at Newegg, it is a low-profile controller that plugs right into the PCI Express x4 slot. It supports RAID 0/1/5/10 and JBOD and a maximum of four hard drives can be connected to the controller. In addition, the controller supports features such as NCQ, multiple logical drive support, BIOS booting support, online array roaming, automatic drive detection, automatic RAID rebuild, TerabyteGuard, and bad sector repair. All version of Windows from 2000 and up (both 32 and 64 bits) are supported, as well as Linux Fedora Core, Red Hat Enterprise / CentOS, SuSE), Mac OS X 10.4.x and above, FreeBSD, and Linux Open Source. HighPoints has also bundled the card with WHQL drivers which means it can be installed under Vista 64bit without worrying about the digital signature warning. For more information, head to HighPoint Technologies’s website.

TEST CANDIDATES

Fujitsu MBA3073RC

The MBA3073RC is Fujitsu’s top of the line SAS drives with a rotational speed of 15,000 RPM. Three storage capacities of 73.5 GB, 147 GB, and 300 GB are available to choose from. The unit we have received is the MBA3073RC, which is the 73.5GB version with 16MB cache. The drive has an average 2.0ms of latency time and average 3.4ms read and 3.9ms write seek time.

Western Digital Green Power WD500ABPS

WD5000ABPS is Western Digital’s new Green Power line of hard drives.  The hard drive is aimed for the enterprise environment which features capacity up to 1 TB. The hard drive has 16 MB of cache, and a maximum transfer rate of 300 GB/s at 7,200 RPM rotational speed. The unit we received is the 500GB version which features 8.9 ms of average seek time.

Western Digital states that the hard drive consumes an average of 4-5 watts less power than the competitor drives.  The unit features IntelliPower, IntelliSeek, IntelliPark, Active Power Mangement, StableTrac, RAID specific time-limited error recovery, and rotary acceleration feed forward.

TEST CONFIGURATION

 

Test Platform

Processor

AMD Phenom X3 8750

Motherboard

Asus M3N78 Pro

Memory

2 GB (2 x 2 GB) Super Talent T800UX4GC5

Drive(s)

  • 2 x Fujitsu MBA3073RC RAID 0
  • 2 x Western Digital WD500ABPS RAID 0

Controller

HighPoint Technologies RocketRAID 2640×4

Graphics

XFX GeForce 8800GTS Fatal1ty

Cooling

Thermalright SI-128 with Scythe S-FLEX SFF21F

Power Supply

Enermax Galaxy 850W

Display

Acer AL1716BBD

Case

None

Operating System

Windows Vista Ultimate 64-bit, SP1

ATTO

SAS

SATA

It is quite obvious that the SAS drive has a better read than the SATA hard drive. The write performance for the SAS is also faster. The better write performance is more prominent with small transfer size. The performance differences has been reduced with larger transfer size. We see an oddity at 32KB transfer size where SAS drives display an unusually poor write performance.

HD Tach

SAS

SATA

The SAS drives are able to offer 81% faster burst rates and 87.6% better average read than the SATA hard drives. Not only that, but they are also able to reduce the random access time by more than 50%. There is a slightly higher CPU consumption for the SAS drives but it is nothing to be concerned about considering users who will run these drives will most likely have a quad core processor at fast clock speed.

PCMark VANTAGE 64

PCMark Vantage is a synthetic benchmark designed to mimic common desktop usage with a series of tests. It is composed of six Scenario suites based on a collection of actual real-world end user applications. From Vantage:

Each test suite contains a subset of the following tests as applicable: data encryption, decryption, compression and decompression, GPU and CPU image manipulation, image import, video playback, editing and transcoding, audio playback and transcoding, GPU and CPU game tests, game data loading, web page rendering, mail operations, media player operations, contacts search, text editing and applicable HDD tests.

 

It is quite a big surprise to see the results from PCMark benchmarks. With the faster hard drives, we get a whopping 187 more points in the overall score. Also, look at each individual score, we can see that across the board, the faster transfer speed offered by SAS hard drives is able to help with the system’s performances. The only exception is the TV and Movies benchmark. After careful examination, we can see that in the HDD Windows Media Center, the SAS is somehow having a significant lower performance than the SATA hard drives. In fact, the same result can be seen under the Productivity benchmark as well (where the software also tests the Windows Media Center test).

We can see that the faster SAS drives are able to offer 28% performance gain over the SATA drives in the overall score. Surprisingly, we also see a huge gain in the Gaming and Productivity benchmark. I believe this can be attributed to the need of data accessing with those applications.

WINDOWS BOOT

Boot up time was tested with the hard drives containing the operating system set as primary boot device. I whip out my trusty timer and measure the time it took for the system to boot into Windows from a hard boot. The system only has Windows with service pack 1 and the essential drivers installed. The tests were conducted three times and the average is reported. Due to the fact that the system would need to detect the external controller and the hard drives, the boot time would be slightly longer than without the external controller.

No surprise here, SAS hard drives running at 15,000 RPM were able to boot the system faster than the SATA hard drives running at 7,200 RPM. On the average, it is about 5 seconds faster.

GAME LOAD

I installed a couple of games, World in Conflict and Company of Heroes, and with my trusty timer again to measure the loading time for each game. I let the games load all the way until they reached to the game option menu page. Normally, most users probably will bypass the initial loading cut-scene. But for the purpose of consistency, I let the games run its normal loading with the cut-scene. Two measurements are recorded. One being the initial launch after Windows boot, and the other is the subsequent loading after the initial boot. The reason two measurements are taken is because the first time any application is launched, it will take longer than any subsequent loading due to the need to transfer data to the RAM. Each test is measured three times and the average is reported.

It’s obvious that by having a faster hard drive, the system is able to feed data to the GPU and CPU when the game is first loaded.  After initial loading of data to the RAM, the subsequent load does not see a dramatic increase in the loading time.

GAME PERFORMANCE

Just for fun, I also use the benchmarks built in each game to measure the performance. The games are set at 1280×1024 with all the settings set to highest level with no AA or AF, and if the game supports DirectX 10, it is run with it enabled.

 

Company of Heroes shows a slight gain with faster hard drives. Despite all things being equal, it is a bit surprising to see a slight performance gain with faster hard drives when it is expected that games usually are more GPU and CPU dependant. World in Conflict does not show any performance gain with SATA and I do believe this is primarily due to the shorter benchmark which does not use the hard drive as much as the longer testing period found with the Company of Heroes.

PERFORMANCE SUMMARY AND THOUGHTS

Feature/Specification

 % Gain
PCMark Vantage X64 Overall Score
3.41
PCMark–Memories 
2.01
PCMark–TV and Movies 
-14.37
PCMark–Gaming 
21.70
PCMark–Music 
8.41
PCMark–Communications 
1.71
PCMark–Productivity 
25.41
PCMark–HDD
28.22
 
 
Windows Boot Up  

4.80
Game Loading (initial/subsequent) 
 
CoH Loading
11.04/0.25

WiC Loading 
1.63/0.78
 
 
Game Performance 
 
CoH Average FPS 
2.76

WiC Average FPS 
0.00
 
 
HD Tach 
 
Burst Speed
77.16
Average Read Speed
87.63
Random Access 
60.78

Let’s take a moment and look at the performance gain by upgrading to the SAS. It is obvious that by going with the faster RPM SAS drive, users will definitely be able to notice the performance increase. PCMark shows that in common desktop usage that puts a heavy demand on the hard drives, such as productivity and gaming, users would notice a 20% gain in the performance. Our real world testing of the Windows boot and Game loading also shows that users would be able to enjoy the faster application loadings. Not only that, Company of Heroes also shows a 2% performance gain by simply going with the faster hard drives.

The limitation of using SAS drives at the moment is the fact that rarely any of the desktop motherboards are able to support SAS hard drives from the getgo. However, the good news is that there are budget expansion cards that can be purchase, such as our HighPoint Technologies RocketRaid 2640×4 that was used in this test, which goes for a retail price of $149.99. This would be a small but very good investment considering that it comes with four SAS ports and supports RAID 0/1/5/10 and JBOD. Another limitation with current SAS drives would be the drive capacity. Currently the highest SAS drives with 15,000 RPM can be found at 300GB, it looks pale compare to the 1.5TB SATA drives. However, if you consider the performance drive of the 10,000 RPM VelociRaptor which also has the maximum capacity of 300GB, the capacity may not seem as a big issue.

Price would be another factor for enthusiasts who are interested in using SAS drives. As we have pointed out, SAS drives do cost significantly more compared to the 7,200 RPM SATA drives. But once again, when we compare them to the 10,000 SATA drives, the gap has been narrowed to less than $100. So, for those who are looking for the highest performance system, SAS hard drives would be a good alternative instead of the VelociRaptor. The budget pricing of the SAS controller, such as HighPoint Technologies RocketRAID 2640×4, has dramatically lowered the cost of moving to SAS drives and making upgrading to SAS affordable to enthusiasts.

It is a well known fact that in some applications and working environments, the hard drive’s transfer speed is the biggest bottleneck of the system. Users who are doing a lot of encodings, data transferring and streaming, and hosting servers would definitely benefit from the higher IOPS, faster sequential performance time, and transfer speed. In addition, as our benchmarks also suggest, even for gaming enthusiasts, SAS drives do help out with the frame rates and game loading as well. For the hardcore gamers who absolutely desire to have the fastest system available, it may be worth to spend the extra cash and pair a SAS controller with 15,000 RPM SAS hard drives to get the most performance possible if cost is not a major concern. Clearly SAS drive is not for everyone but it would be something that enthusiasts may consider.

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