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Written by Bruce Normann   
Tuesday, 07 February 2012
Table of Contents: Page Index
QNAP TS-879U-RP NAS Network Storage Rack Server
QNAP v3.5 New Features-Home
QNAP v3.5 New Features-Business
Closer Look: QNAP TS-879U-RP
Insider Details: QNAP TS-879U-RP
Technology Details: QNAP TS-879U-RP
QNAP Turbo NAS Features
QNAP TS-879U-RP NAS Hardware
QNAP TS-879U-RP Software
QPKG Center Software Expansion
NAS Testing Methodology
Basic-Disk Test Results
RAID 5 Test Results
NAS System Overhead Measurements
NAS Server Final Thoughts
QNAP TS-879U-RP Conclusion

NAS System Overhead Measurements

I've discussed the potential impact the NAS hardware has on performance in general terms so far. The hard reality is that the CPU, drive controllers, memory, and network subsystems have a direct and profound impact on the throughput of a NAS device. In extreme cases where multiple drives (4+) are arranged in higher-order RAID configurations, the CPU has a ton of work to do, calculating parity bits and parsing them out to multiple data streams. In-line data encryption adds another potential load to the infrastructure. In this section, I'm going to look at some results from the System Monitor capability that is available on the QNAP Turbo NAS server.

Let's start off looking at CPU usage on the NAS server. During a straight data transfer from the PC to 4 disks configured as RAID 5 on the TS-879U-RP, the results show the Intel Core i3-2120 CPU coasting along at close to 25% on both cores, with the additional "hyper-threaded" cores doing close to nothing. They're involved, but only in a peripheral way. This is in marked contrast with every other NAS I've tested, where the CPU is maxed out at 100% when doing anything involving RAID. The Intel Atoms hold their own for the most part, but the Marvell processors have been a major bottleneck in my experience. Finally, with this corporate beast, we have a CPU that can handle the load. The memory subsystem on the QNAP TS-419P II is not being taxed by these file transfers at all. It's not even worth looking at the chart.

QNAP_TS-879U-RP_Turbo_NAS_Server_10-x-1GB-RAID-5-CPU.jpg

The host system is also tooling along at about 25% on the CPU (use the green trace in every graph below...), barely breathing hard. The Disk subsystem is having an even easier time of it, cruising at less than 15% of its throughput capacity. It's what you would expect for a 3d generation SSD capable of transferring over 500MB/s of data in sequential tests. The Network trace is where we see the real issue. That GbE NIC is working overtime and still can't keep up! I'm sad to say, we are completely limited in this test set by the network interface. It's maxed out and we aren't going to get any more, unless we spend an additional $1,000 on a new pair of 10GbE NICs from Intel.

QNAP_TS-879U-RP_Turbo_NAS_Server_10x1GB-Single-Disk-Resource.jpg

Let's take a look at the network interface on the NAS side. This particular chart was produced during five disk-writing tests, with both Ethernet connections set up for for teaming via IEEE 802.3ad/Link Aggregation. The first thing to inspect is the green trace, which shows Packets Received by the NAS. Since this was a "Write to NAS" test, you can see that the data throughput into the NAS is pretty well maxed out on the Ethernet 2 connection, at 116.1 MB/s (929 Mbps). Over on the Ethernet 1 connection, you see much less data being sent from the NAS back to the host computer, only 1.7 MB/s. This is likely just housekeeping data, checksums and such. So in theory, teaming the two GbE NICs together allows for double the network throughput; in reality it only does that if you have equal amounts of data being transferred IN and OUT of the device. In real-world usage that's a distinct possibility for some applications, but in my experience many data storage systems get hit asymmetrically all the time. In a typical tech office, everyone needs to check their work out of the "vault" when they get started in the morning, and they all need to check it back in before they leave for the night.

In an earlier review, I said, "One day, I'm going to load up one of the big NAS units with high end SSDs in RAID 0 and let it rip; then we'll see where the system bottlenecks are." Well, here it is: it's the industry standard network interface that's holding the big rigs back. Once a pair of 10GbE NICs are brought onto the team, I'm sure the load will balance out and the other team members will be pulling more weight.

QNAP_TS-879U-RP_Turbo_NAS_Server_10-x-1GB-RAID-5-GbE-x2-Team.jpg

Just to show the contrast between the TS-x79 series and the lesser models in the product line, take a look at the CPU utilization from an earlier test. The NAS CPU is being taxed to the max during these file transfers, with either small numbers of large files or a large number of small files. In the chart below, you can see some occasional dips where individual, smaller files were transferred. The system buffers are getting bounced around during this scenario and you see some sharp drops, with a corresponding sharp recovery. There's nowhere for the CPU to hide in a high performance NAS appliance, and the ARM processor in QNAP's lower-priced models gets hammered pretty bad in typical use cases.

QNAP_TS-419P_II_Turbo_NAS_Server_1x10-the-10x1-cpu

Finally, I give you a glimpse at some further testing I plan to do on the TS-879U-RP. I reformatted all eight drives in RAID 5, but this time I selected the option to encrypt the data to AES 256-bit standards. Now, during the disk write tasks, the CPU gets a little more of a workload. Reading the encrypted data doesn't tax the system as heavily, as far as I could see. In the CPU chart at the beginning of this section, you can see that CPU 2 and CPU 4 were just along for the ride; there was nothing for them to do. With data encryption in the mix, the load on them is much higher, spiking up to 100% quite often. Remember that these are virtual CPUs, as the Intel Core i3 2120 CPU has only two physical cores, but it supports Hyper-Threading. Also, the Core i3 does not support the recent AES-NI enhancements, so it's using brute force to encrypt this data. With the GbE interface keeping the throughput artificially low, it looks like the CPU still has some headroom left.

QNAP_TS-879U-RP_Turbo_NAS_Server_AES_Write_01.jpg

I hope this section showed you some objective reasons why the infrastructure that any NAS product brings to the table is important to its overall performance. As the number of drive bays goes up, the hardware requirements increase as well, and the price has to follow. I know it's disheartening to see that you don't get great economies of scale on the larger NAS units, but it would be even more of a shame if they didn't perform up to their true capabilities because the hardware was holding them back. In this case, the network interface is definitely holding the system back, and I hope to rectify that in the future.

Now, let's look at some Final Thoughts, and then move on to our Conclusion and Product Ratings.



 

Comments 

 
# I3 with AES-Ni ?Moogle Stiltzkin 2012-02-16 02:29
Since when did Intel I3's have AES-Ni instruction ?

QNAP currently only has 2 rack models with the x79 name that has XEON cpus which do have AES-Ni.

But the other X79 models only have Intel I3 cpus, and last i checked they didn't have AES-Ni instructions on them ..... yet your saying otherwise ? Got any references for that ?

However despite that, Jason from QNAP is claiming their tests on the 879U-RP with AES encryption could achieve 100MB/s in both read & write in Gigabit environment.

His a trustable guy so i'll believe that :X but what i doubt is your claim that i3 cpus have AES-Ni ....
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# Face Palm...Bruce 2012-02-16 06:08
Just looked it up on Intel site, and you're right. There are 141 products with AES-NI. No i3's though.
ark.intel.com/search/advanced?AESTech=true

Well, I've got some re-writing to do....

FWIW, my initial testing with AES-256 supports Jason's claims. The GbE bottleneck is the dominant factor.

Thanks for pointing this out.
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# RE: QNAP TS-879U-RP NAS Network Storage Rack ServerMoogle Stiltzkin 2012-02-16 06:35
yeah, all that matters is the result. doesn't matter if it has AES-Ni or not (although it's good to have since it's suppose to accelerate AES encryption so why not) since all comes down to whether it can perform well even with AES 256 encryption enabled.

Jason says it does 100 mb/s and that in my opinion is very good. I was worried and confused why they opted for the i3's which are basically almost the same as i5's but without the aes-ni. But from the results, seems my worries were unfounded ? As i was expecting results like these which was an article by tomshardware showing how bad performance was on many NAS brands across the board that didn't use encryption acceleration such as AES-Ni.

##tomshardware.com/reviews/nas-encryption-aes-ni,2873.html


Anyway i wonder if you would be kind enough to add to your review, a chart showing AES 256 encryption performance of the i3 QNAP to help back up Jason's claim. I trust Jason, but other people who don't know him will want proof from third party sites like yours to see if what QNAP claims is true or not.

I'm also interested to know whether the other i3 QNAP models such as the 1079 can achieve the same good results for aes 256 encryption, as well as compare the results with Synology Diskstation DS3611xs which sports a Intel® Xeon® Processor E3-1225 cpu.
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# Follow-Up testingBruce Bruce 2012-02-16 07:07
Yes, I plan to do a follow-up article which will focus on performance improvements with the optional 10GbE interface, and to document the AES-256 performance. Take a look at the last chart in the NAS System Overhead Measurements section of this article. That's one of the tests I ran with AES-256 enabled, and the CPU looks like it still has some headroom left, when running of the Gigabit interface. I'll have full results in the follow-up article.
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# RE: QNAP TS-879U-RP NAS Network Storage Rack ServerMoogle Stiltzkin 2012-02-16 06:44
Quote:
FWIW, my initial testing with AES-256 supports Jason's claims. The GbE bottleneck is the dominant factor.


And lets not forget conventional hard drives may also be a bottle neck ?


The fastest read and write maximum throughput for a hard drive is Seagate's New Barracuda 3TB (ST3000DM001)

##anandtech.com/show/5042/seagates-new-barracuda-3tb-st3000dm001-review


Read Throughput Maximum: h2benchw 3.16
193.55
##tomshardware.com/charts/hdd-charts-2012/Read-Throughput-Maximum-h2benchw-3.16,2900.html


Write Throughput Maximum: h2benchw 3.16'
191.47
##tomshardware.com/charts/hdd-charts-2012/Write-Throughput-Maximum-h2benchw-3.16,2903.html
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# 8xBruce Bruce 2012-02-16 07:12
I'll be running RAID 5 with eight drives, though.

I don't expect to reach the same speeds that QNAP did with (8) Intel SSDs, but I'm betting it will still be way above what the unit does with the Gigabit interface.
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# RE: QNAP TS-879U-RP NAS Network Storage Rack ServerMoogle Stiltzkin 2012-02-16 07:11
regarding your last con, well some desktop drives can be used fine for raid.
For me, i've used 6 x SAMSUNG HD203WI for a long time and they work fine on my QNAP ts-659 pro II.


QNAP and other branded NAS, tend to ignore tler, so it's not critical for these nases when using raid seeing as it's not being used.

Quote:
The responses I received from Synology, QNAP, NETGEAR and Buffalo all indicated that their NAS RAID controllers don't depend on or even listen to TLER, CCTL, ERC or any other similar error recovery signal from their drives. Instead, their software RAID controllers have their own criteria for drive timeouts, retries and when a drive is finally marked bad.

##smallnetbuilder.com/nas/nas-features/31202-should-you-use-tler-drives-in-your-raid-nas


however samsung has sold off their hard drive business to Seagate who bought their hd unit out.

So the only other manufacturer that offered some good desktop raid drives was Hitachi i believe which was the Hitachi Deskstar 7K3000 3TB which is a desktop drive that works fine in raid for say a QNAP.

##storagereview.com/hitachi_deskstar_7k3000_3tb_review_hds723030ala640


The desktop drives you should be wary about for using raid are western digital and seagate, which intentionally make it problematic in a raid setup, by dropping out very often to make you buy their x2 expensive raid edition drives.
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# Some work fine.....Bruce Bruce 2012-02-16 07:44
The Spinpoint F3 was a favorite for NAS use, no doubt. Other readers have also reported good luck with their Hitachi Deskstars. You'll see similar reports on the QNAP support forums. I'm somewhat concerned that most reports are from users with smaller NAS units, where the combined vibration of 8-12 drives is not present. It's bearing failure, as much as controller quirks that cause HDD failures.

Samsung drives are still being built to the old designs/specs for now, right? Get them while you can, I think....
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# The 20 should be closser to 2. bits vs Bytes.tygrus 2012-02-22 03:05
"twenty times faster than what the latest generation of SSDs can muster"
Sorry but 10GbE =
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# Comment system ate my commenttygrus 2012-02-22 03:41
There was some mathematical symbols in my previous comment. The comment has been truncated.
...
10GbE =lt 1250MBps. 500MBps = 4800Mbps.
Reasonable sound level for a device to be in a server room.
Too loud for home use.
Would like to see aditional testing with multiple clients or larger queue depth. Need to beg someone for some 10GbE hardware.
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# 10GbE is comingBruce 2012-02-22 06:00
Next week I'll have two Intel 10GbE NICs. I'll just have the one PC, but would RoboCopy, with it's multithreaded operation get closer to the multiple client scenario?
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# Updated Results in New ArticleBruce 2012-03-21 08:00
Just wanted to let all of you know that I completed the additional testing, with 10GbE NICs and a RAM Disk on the PC.

Wow! What a difference.

Check out the results in my follow-up article here: benchmarkreviews.com/index.php?option=com_content&task=view&id=882&Itemid=70
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# RE: QNAP TS-879U-RP NAS Network Storage Rack ServerMoogle Stiltzkin 2012-03-21 08:09
Nice :} just read it.
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