Should You Use TLER Drives In Your RAID NAS?

[Tarrant1701]

Hi all,
I was hoping you can answer a question for me. As you know, TLER is important for RAID sets to prevent dropouts due to prolonged error recovery attempts.

However, if you look at hardware compatibility lists for QNAP devices (and other brands), they include both enterprise and desktop (non-TLER-enabled) drives. What is also not clear is if the RAID implementation in NAS devices also support TLER.

My question then is, what is your take on this? Does QNAP TS-509 pro or similar class devices support TLER? Is it worth spending the extra $$$ for TLER drives in these devices if not supported?

Thanks!

 

[claykin]

Its not so much of supporting or not supporting TLER. All TLER does is make sure the disk does not go longer than 7 seconds before sending a message to the RAID controller and suspending future error recovery for a few moments.

Desktop class drives do not include this 7 second timer and can continue to correct errors for longer than 7 seconds. With a typical RAID controller once 8 seconds is reached and the disk has not responded with a message, the controller considers the disk dead and drops it from the RAID.

NAS vendors are approving several desktop class drives, so its fairly safe to assume that they have watched the error correcting behavior of these drives and adjusted their RAID controller timer accordingly to allow these drives time to complete typical error recovery. Its also very likely that they have implemented parameters to adjust the way the controller handles error recovery based on the drive you install. This is another reason why its best to use a drive thats been tested and approved by the NAS vendor.

In my opinion its best to use drives with a TLER type feature to ensure best reliability with RAID controllers. Yes these drives are more expensive, but they are often built better and with better quality components. Not always, but often. My preference is Seagate ES.2 or Constellation drives.

 

[thiggins]

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

 

[john4200]

Desktop class drives do not include this 7 second timer and can continue to correct errors for longer than 7 seconds. With a typical RAID controller once 8 seconds is reached and the disk has not responded with a message, the controller considers the disk dead and drops it from the RAID.

I think it is a bit more complicated than that.

Most hardware RAID controllers, when they try to read from a drive, will wait about 8 seconds for a response. If they do not get one, then they will regenerate the data from redundant data on other disks, THEN will try to write the data back to the disk that failed to read in 8 seconds -- the idea is to force the disk to remap the bad sector to another one (most drives have a small pool of extra sectors for just this purpose). But if the drive has gone into deep recovery (still trying to read the bad sector) and does not respond to the write request, THEN the controller will usually assume the drive has failed and drop it from the array.

If a drive supports TLER, ERC, CCTL, then it will always respond within 7 or 8 seconds, even if a sector cannot be read or written. The RAID controllers will be able regenerate the sector from redundant data, and it will write it back, thus ensuring that the drive logically remaps the bad sector to a different physical sector on the platter.

 

[claykin]

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

Tim, you are the man! Excellent write-up.

 

[thiggins]

Tim, you are the man! Excellent write-up.

Glad you liked it.

 

[claykin]

Glad you liked it.

I posted a link to your article on the Readynas forums and received a reply from one person who wished you also discussed other benefits of Enterprise drives.

http://readynas.com/forum/viewtopic.php?f=24&t=43250

 

[Moogle Stiltzkin]

So basically, the tler for raid certified drives isn't a necessity for those Nases e.g. QNAP. That is good to know.

But, raid certified drives usually have tech like my Western Digital RE3 such as

Too much environmental vibration can knock the drive head off course, slowing performance in the process. Since IntelliSeek can only reduce vibrations rather than eliminate them completely, the RE3 employs Read Ahead Fast Forward (RAFF) tech that monitors both linear and rotational vibration and adjusts the drive head's position accordingly. Western Digital claims that this latest RAFF implementation boosts the RE3's performance by 60% over the previous generation RE2 in "high vibration environments."

To further protect the RE3 from environmental hazards, WD has equipped the drive with a multi-axis shock sensor similar to what you'd find in a mobile hard drive. This sensor is designed to compensate for physical shock rather than vibration, with an eye toward protecting data from a catastrophic head crash rather than maintaining consistent performance through physical trauma. WD's NoTouch technology also makes an appearance in the RE3, moving the drive head completely off the platter when it's not in use.

Also some are 24/7 certified, most likely because of the features set i mentioned above.



So even TLER is not so important when used for say QNAP Nas, you'd still need a raid enterprise drive for the other features especially for NASes that are left on 24/7

When deployed independently, hard drives are left to perform error recovery on their own while the rest of the system waits. RAID controllers aren't keen to idle, though, and if a drive takes too long to recover from an error, it's often marked as bad and dropped from the array. To prevent premature ejection from an array, the RE3 features Time-Limited Error Recovery (TLER) that, er, limits the amount of time the drive will be unresponsive while attempting error recovery on its own. If the drive can't recover the error within this limited time span, it simply gives up, deferring error recovery to the RAID controller

From my understanding, desktop drives are certified for 8 hours of operational use. 24/7 operational drives require the techs only raid certified drives are bound to have.


I'd honestly stick to the enterprise certified drives imho, since , my QNAP TS-509 Pro usage is 24/7 and the data is important to me.


So anyway, to do justice to this article, it shouldn't solely just be about whether Tler or it's like is a must have for nasses, you need to consider the other tech only found in raid certified drives. And then change article to are raid certified drives really required vs consumer desktop drives that cost half the price. I feel that would be more appropriate.

Otherwise people may just jump to desktop drives without considering other important aspects that raid drives have over desktop drives.

 

[thiggins]

These features usually come on "Enterprise" grade drives (WD Caviar RE series, Seagate Barracuda ES, ES.2, Samsung Spinpoint F1), which are built to take the constant, hard use of business environments. So investing in these more expensive drives is probably a smart move if your NAS is under constant heavy use. But it will be the more robust drive construction and not TLER / CCTL / ERC that will make your RAID NAS more reliable.

I think that properly gives Enterprise drives their due.

 

[mauryg]

Also applies to motherboard RAID

Tim,
Excellent explanation of the problem.
It also applies to RAID systems using the ICH10R controller on many motherboards, referred to as "fake RAID in Linux parlance. I set up a RAID 5 on my ASUS P6T motherboard using Hitachi Deskstar drives. It repeatedly dropped drives. Changed out the drives to WD Cavair Black drives and same problem. Then I discovered the following facts:
1. In the fall of 2009 WD changed the firmware on their Caviar Black drives and disabled TLER. Prior to that they even offered a free utility for setting it.
2. At about the same time, Intel released a new version of their ICH10R RAID driver which apparently did not compensate for the lack of TLER.
There were numerous complaints of RAID failure with the new drivers and I eventually gave up on ICH10R RAID.

Maury

 

[Tarrant1701]

True, there are many considerations and enterprise drives do have a lot going for them. But here are my thoughts:

1. My TS-509 is on 24/7 but not actively used 24/7, meaning that when I go to bed the drives are usually in sleep mode. It is mostly used for backups, archiving, and serving multimedia during the day.

2. Certain "Desktop" drives also have a non-recoverable error rate similar to enterprise drives, eg 1 in 10^15 bits so I definitely stick with those models.

3. I don't need maximum up-time as I do not use my unit in a business environment, so if I have to spend 16 hours rebuilding an array, I can live with that down-time.

4. The cost of a 2TB "Green" drive is roughly 3 times less than the cost of a 2TB "enterprise" drive. Which means that the enterprise drive has to be 3 times more reliable as a desktop drive to be economical for me.

5. Certain brands/models have additional measures to reduce the impact of vibration (if you believe the marketing-speak):

"StableTrac™- The motor shaft is secured at both ends to reduce system-induced vibration and stabilize platters for accurate tracking during read and
write operations. (2 TB model only)"

So for me, I went with the WD20EARS ... I may live to regret that decision, but we'll see

 

[Moogle Stiltzkin]

Thiggins.

I am in a serious dillema.

I am getting a QNAP 659 NAS and wish to use 4-5 x WD1002FAEX drives in it. They are 6 gb/s SATA III drives with 64mb cache each.

My worry is, because they are desktop drives, will the deep error recovery be an issue ??? Or will it not seeing as your article says QNAP software raid takes over regarding error recovery.

Please may i have your input soon because i am getting this within a week.


My planned up time will be 24/7

http://forum.qnap.com/viewtopic.php?f=25&t=33571&p=145211#p145211

 

[thiggins]

I have nothing to add to the information in the TLER article.

 

[claykin]

Thiggins.

I am in a serious dillema.

I am getting a QNAP 659 NAS and wish to use 4-5 x WD1002FAEX drives in it. They are 6 gb/s SATA III drives with 64mb cache each.

My worry is, because they are desktop drives, will the deep error recovery be an issue ??? Or will it not seeing as your article says QNAP software raid takes over regarding error recovery.

Please may i have your input soon because i am getting this within a week.


My planned up time will be 24/7

http://forum.qnap.com/viewtopic.php?f=25&t=33571&p=145211#p145211

If error recovery would be an "issue" QNAP likely wouldn't include that model on the compatibility list. Yes, WD has been claiming better error recovery rate with some of their newer desktop disks, but I'd say the jury is still out on real world outcomes. If this NAS will be mission critical, why not buy enterprise disks? You'll likely sleep better at night. Thats got to be worth a few bucks.

 

[BrianBloom]

If error recovery would be an "issue" QNAP likely wouldn't include that model on the compatibility list. Yes, WD has been claiming better error recovery rate with some of their newer desktop disks, but I'd say the jury is still out on real world outcomes. If this NAS will be mission critical, why not buy enterprise disks? You'll likely sleep better at night. Thats got to be worth a few bucks.

While I would love to be able to use enterprise caliber disks - $280/pop is simply sometimes not in the budget, especially when you are buying two or four of them.

Can anyone offer a recommendation for the "next best" thing, perhaps using under $200 2TB drives? (I'm looking at setting up a DS210j or DS209 system at home - so will still be using RAID most likely but can't afford disks that each cost more than the NAS itself )

 

[claykin]

If I was to choose desktop class disks my first choice is Hitachi. Hitachi seems to have a better track record than either Seagate or WDC.

Just make sure its on QNAPs compatibility list.

 

[Moogle Stiltzkin]

If error recovery would be an "issue" QNAP likely wouldn't include that model on the compatibility list. Yes, WD has been claiming better error recovery rate with some of their newer desktop disks, but I'd say the jury is still out on real world outcomes. If this NAS will be mission critical, why not buy enterprise disks? You'll likely sleep better at night. Thats got to be worth a few bucks.

But don't you see, in QNAP for example, the compatibility list is separated by business (enterprise drives) vs home user (desktop drives).

Compatibility for desktop could just mean that it works in JBOD, but no mention how it would operate in raid, especially concerning issues like lack of tler support. I've already tried their forum but did no get a clear answer when asking how desktop drives lacking tler would work in raid for QNAP.



I do indeed have 5 x 1tb Western Digital RE3s and haven't had any problems with them whatsoever. But due to $$ constraints, this time around i am venturing into unknown waters by going for desktop drives for home usage purposes as many others have been doing. Not only that, but the Samsung spinpoint Ecogreen 2tb i am looking at is 5200 rpm, which after much consideration seems to be a sufficient performer for storage and streaming data purposes; in addition to lower ownership costs as it also consumes less power which is very important to me as i leave my QNAP on 24/7

So my old QNAP 509 would be a back up using enterprise drives, but if desktop in raid was reliable enough, then maybe i can also use the 509 for additional storage as well.



Yes i too have also heard Hitachi desktop drives was well regarded in raid. But Samsung has been getting some positive comments to i hear.

Western Digital not much (in regards to their desktop drives anyway); and Seagate is plagued by high failure rates.

 

[graviton]

Clear as Mud

I have just bought a Synology DS211 which I plan to run in RAID 1 as a home file store/mail server/media server. I remain completely confused about whether to choose desktop or enterprise HDDs to go in my new NAS.

The whole point of running RAID 1 (and most other RAID levels) is to protect against disk failure. I will be sacrificing half my storage capacity to provide this protection. Why should I then also be expected to pay twice price for 'enterprise' HDDs because the desktop hard disks I have kept my home data on for the past 8 years are somehow not good enough for RAID. Surely if one disk fails, all my data is protected on the other disk and the likelihood of two disks failing almost simultaneously is vanishingly small. This is what Redundant Array of Inexpensive Disks is supposed to be all about.

Furthermore I have seen posts on other websites suggesting enterprise HDD are physically identical anyway and the only difference is probably some settings and factory testing.

Please, please can home users have some clear guidance. If I find this nonsense confusing and have 3 degrees and some IT experience, how on earth is Joe Public supposed to buy himself the 'right' HDDs.