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Wednesday, January 16, 2013

RAID - NAS and QNap

2006 QNap launched Turbo NAS TS-101, which is the first NAS with SATA interface in the world, and exclusively provides.
Q-RAID1 configuration for single drive model for data protection.
QNAP Systems, Inc., as its brand promise "Quality Network Appliance Provider", aims to deliver comprehensive offerings of cutting edge network attached storage (NAS) and network video recorder (NVR) solutions featured with ease-of-use, robust operation, large storage capacity, and trustworthy reliability. QNAP integrates technologies and designs to bring forth quality products that effectively improve business efficiency on file sharing, virtualization applications, storage management and surveillance in the business environments, as well as enrich entertainment life for home users with the offering of a fun multimedia center experience. Headquartered in Taipei
How to recover NTFS data from HDD after insertin into NAS?
HDD Spin Down (HDD Standby)
WD Desktop drives (Green/Blue/Black) are not recommended
The WD Desktop drives (Green/Blue/Black) are not recommended for RAID volume usage, as the following issues has been realized.
1. Slow performance
2. Disk drop out from RAID easily
3. Read/write error on file system 
According to the reply from WD manufacturer. 
Q:Are WD Desktop drives (Green/Blue/Black) good for RAID systems?

A:You may need to know if the NAS controller works with drive that have the TLER disabled, or the TLER needs to be enabled on the drive. However, we do support these drive on computers only, but not on RAID environment, please see the RAID enabled drives in the link below: (Enterprise Drive)
We have add the WD Desktop drives as the not suggested HDD on HDD compatibility List 
The HDDs have passed QNAP lab's initial verification of compatibility. However, because the HDD manufacturer has suggested not to use the desktop HDDs in RAID subsystems and some users have reported unstable experience with these HDDs, we do not recommend using these HDDs with QNAP products."
The best hard drives for Intel's PCH RAID

WD RE(RAID edition) disks definitely have TLER. [...] 689-7.html
Even some desktop edition WD disks used to be "TLER available" via the TLER utility, and that is before WD decided to widen the gap between Desktop disks and Server RAID ones in the beginning of this year.
I'm looking for a more reliable RAID solution, but of course faster is always better. For example, maybe I should just pick a RAID card which is marked CCTL compliant and then pair it with CCTL ready drives to achieve the RAID stability. Any suggestion on which to choose from, CCTL, TLER or ERC? or SAS maybe?
users assembled a RAID using WD's Caviar Black series, which do not support time-limited error recovery ("TLER" ).
Yes, they will drop out of the RAID array after they start to fill up, because the firmware's error recovery logic may take too long,
and Intel's I/O controller hub will conclude that one or more HDDs are not responding.
BEST WAY is to stay with WD's RE (RAID Edition) HDDs, which are designed with TLER --time-limited error recovery.
The specs for each WD HDD will state if TLER is supported by any given HDD.
Yes, with WD RE hard drives and Intel I/O controller hubs' reputation and prevalence, I shouldn't worry too much about their incompatibility.
Just like you thought, TLER will most likely help lessen the chance for hard drives to be dropped from a RAID array. This has also been mentioned by an Intel engineer.
However, by looking at these reported problems:
"Random drive fails with new Matrix Storage Manager 8.9"
"Random drive fails with new Rapid Storage Technology 9.5 ?" [...] 0&tstart=0
I am afraid WD RE TLER enabled disks will only alleviate the drop-out sympton somehow instead of providing a rock solid array, because even though they will be more responsive to ICHxR/PCH but may still not be a perfect match? The Intel support engineer told me that ICHxR/PCH does not truely support TLER/ERC/CCTL. He can't provide me a list of compatible hard drives for ICHxR/PCH.
I searched through Intel site for tested and supported parts for the PCH motherboards but failed to find info regarding compatible/tested hard drives. Tested memory is listed nonetheless. [...] 029945.htm
I think two things can help assure the stability of matching ICHxR/PCH with TLER/ERC/CCTL drives:
1. Even though Intel's integrated RAID solution may not claim to be the perfect match for any specific vendor's(or vendor group's) standard but it should still claim categorically compatible to the extent that ICHxR/PCH is guaranteed not causing drop-out problem due to the prolonged disk's error recovery process(e.g., 5~10 seconds) as long as these disks have implemented TLER/ERC/CCTL.
2. Some compatibility list of hard drives for the ICHxR/PCH boards
I read the threads and it appears that version 9.6 fixes the issues reported with 8.9 and 9.5. It also looks like using RE drives wasn't as bad as using Caviar Black drives. What will you do? Buy a RAID controller, use version 9.6 or no RAID at all? Edit: SAS drives are not more reliable that SATA drives, but they are faster. When connected to a good RAID controller with a BBU, writing is very fast. Just add more drives to improve performance.
From a scientific point of view, controlled tests need to compare all permutations involving all IDE, AHCI and RAID modes with and without TLER (or similar) support in the HDDs attached.
And, with or without Intel's ICHxR chipsets, there is also the option to create "software RAID" arrays with Windows XP e.g. starting with dynamic disks.
Thus, IDE and AHCI can still be configured in such a software RAID.
We have 2 x 6G WD HDDs configured as a software RAID 0 (for speed); each is 1TB for a total of 2TB; and, this RAID 0 array is far from being full :)
Here's that 6G HDD: [...] 6822136533
So far, so good; and, it's pretty fast too!
The following test was done with a 96MB file,
to force the test to read from the 2 HDD caches only,
in order to get a feel for the 6G difference (if any):
[Read more at link!] [...] anguage=en
p.s. WD has sold so many millions of HDDs in recent years, and Intel's I/O controller hubs are also so ubiquitous, it's extremely unlikely that WD's RAID Edition HDDs are incompatible with any recent ICHx.
TLER/ERC/CCTL capable drives needed for PCH RAID
The drives are clearly targeting different market segments, the RE drives are for servers with heavier load and they also come with five rather than three years warranty.
I guess it comes down to what you're using your NAS for and how much the extra warranty period is worth to you.

The fact that we test drives doesn't mean that you won't run into problems, they are after all mechanical devices that are spinning disks are silly high speeds, so things can go wrong.

The main differences in specifications are: 
  • Spin speed - WD RE [RAID Edition]spin at 7200 rpm and WD Red use an unknown variable spin speed with the marketing name IntelliPower (probably somewhere closer to 5400 rpm).
  • MTBF - WD RE are specified at 1.2 million hours and WD Red are specified at 1 million hours.
  • Error rate (non-recoverable bits read) - WD RE are specified at 1 in 10^15 and WD Red are specified at 1 in 10^14.
  • Warranty - Real enterprise disk have a 5 year warranty. WD Red have 3 years.
...and if the red drives are better than desktop drives or those dredded green drives, how much so?
Again, I'd say that it is almost impossible for any human to quanitify that but I'll have a shot at it and say they are 27096.4 % better. Considering that WD Green have given a huge majority of NAS/RAID users nothing but problems and WD Red so far have an excellent reputation, the difference must at least be gigantic.

What we do know is that WD Green have a crippled firmware, intended to make them unsuitable for NAS/RAID applications, while WD Red have a firmware intended for that specific use. That is a very, very important factor! According to marketing, WD Red also have a balance/vibration control (3D Active Balance Plus) that the average desktop disk may not have. But I'm no disk expert and don't know enough to make any definite claims about.

I do know that WD Red are extremely quiet compared to moste other desktop disks.
i plan to back up the nas periodically...
Yes, all important data needs to be backed up on separate systems regardless of the reliability, quality and price of the main storage (that includes also all enterprise products WAY above the market segments Qnap are covering).
...but even so i dont want to run into [problems a year down the track like i have with the seagate 5900 drives that were meant to also be on the supported list.
Yes unfortunately it took a while for the compatibility problems to show. :cry:

WD Red have only been available for 5-6 months for mere mortals but I believe the problems showed much, much earlier that that with both WD Green and ST2000DL003.
also are these red drives similar to the green ones? in that they run at a slower speed etc.
...i think that was a major problem in the nas fo the green drives.
I absolutely don't think the spinning speed was ever the issue with any Green disk, it is other things that cause the problems. Do remember that the problems have mainly been with "Green" disks from WD and Seagate. There are examples of slower spinning disk models from both Samsung and Hitachi that have a very good reputation among Qnap users. what has wd done with these reds to improve things and market them to be used in the nas?
Well for starters giving them a firmware specifically intended for NAS usage instead of being deliberately crippled...
Finally, i have read that having a mix of drives is better than all drives from the same model/batch.
Yes the theory is that in a RAID-volume you definately don't want disks failing extremely close to each other in time, as that may lead to more concurrent disk failures than the selected RAID-level can tolerate without data loss. Having all different disk models (or from different batches) and sourced from different suppliers would be the optimal configuration in that regard. How important that is, is however another matter.

Personally I think that the theory have some merits but it's importance shouldn't be overrated and personally I definately don't follow it religiously. There are also several other important factors in the equation. If you want to optimize in this regard, I believe that different suppliers (mostly to make sure the products have had a different handling in transportation), different batches and different disk models are important in that order.
i wonder what people think about mixing two wd re drives with two wd reds? is that going to be problematic?
It should be possible to mix any compatible disks listed on the Qnap disk compatibility list.

"Bitmap" enables faster RAID rebuild time due to a drive crash or plugged out (recover from degrade mode to normal mode).
Bitmap only works in RAID 1, 5, 5+hotspare, and 6.

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