Question

Enabling NCQ on alreay use harddisk (RAID 5)

Asked by: zacker69

Hi,

I just want to know if I can enable NCQ on harddisk that is already used. I have harddisk and controler that support NCQ and I want to check if it will give more speed but I want to be sure that it is not dangerous for the data to enable it while data is on the disk. I have 4 disk configure with RAID 5. Is it dangerous? Does I need to format  the drive to use NCQ? Does somebody try it with raid 5 and saw more performance?

Thank you!

Dany

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Asked On
2009-09-14 at 06:12:58ID24729409
Topics

Computer Hard Drives

,

Computer Servers

,

Hard Drives & Storage

Participating Experts
3
Points
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Comments
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Answers

 

by: gikkelPosted on 2009-09-14 at 08:20:49ID: 25326374

You shouldn't encounter any problems at all if you enable NCQ...there really isn't a way to properly benchmark NCQ and you won't notice any significant boost in performance.  Many times you'll see benchmarks with results that are actually decreased with NCQ enabled.  However, it will provide better performance in certain instances (under high i/o) and should increase the life of the disk (in theory).  In short, it may not be worthwhile...but there's no harm in trying.

 

by: meyersdPosted on 2009-09-14 at 16:50:57ID: 25330280

If you have SCSI disk drives, they're already using NCQ. If you have SATA II drives, they use a cut-down version of NCQ and both the controller and drive must support SATA II NCQ. If you have SATA I or ATA drives, you're out of luck as they don't support any form of NCQ.

If your drives and controller support NCQ, then yes, you can switch it on without affecting data on the drives. Note that if you have SCSI (or FC for that matter) drives, you can't turn it on as it;s already running as part of the SCSI protocol.

 

by: dlethePosted on 2009-09-14 at 23:41:10ID: 25332301

If the disks are attached to a HARDWARE RAID5 controller, then do NOT enable NCQ.  You run risk of losing data.  Some of the chipsets that many raid controller vendors use had a bug relating to NCQ and losing data, so the fast solution that the vendors used was to disable NCQ.


But i expect you use software RAID.   Your O/S kernel is critical, especially if running LINUX, there are numerous bugs reported with various controllers & kernel combinations that resulted in data loss with NCQ.  


NCQ is a configurable parameter that is non-volatile, so you can turn it on/off at will without affecting data.   In a RAID configuration, especially RAID5, then the benefit is a function of block size, and if it is a typical RAID5 mix of reads/writes large & small I/O, then you probably won't see any difference.  I personally wouldn't enable NCQ in a RAID5 configuration, especially with SATA disks.  You could probably get much better performance by tweaking O/S settings instead.

 

by: meyersdPosted on 2009-09-15 at 00:21:31ID: 25332503

>If the disks are attached to a HARDWARE RAID5 controller, then do NOT enable NCQ
That's worrying. Could you provide more information especially regarding hardware vendors and drives affected? NCQ is part of the SCSI spec, so a major bug in RAID controller firmware such as this is important.

 

by: dlethePosted on 2009-09-15 at 00:49:06ID: 25332655

Sorry, I am not allowed to provide that information.  I have NDAs with many of the vendors, so am speaking from experience.  You should have no problem googling NCQ with data corruption, bug, and RAID and get an idea.  

What you fail to realize is that RAID vendors tweak disk settings all of the time.  The high-end vendors even load their own firmware on disks so they have complete control.  The only bone i will throw you is that there are a handful of manufacturers who make SAS/SATA chips that do the protocol work, and one of them had a firmware bug that was not correctable via flashing, so a lot of manufacturers had to go back to the drawing board and either spin a new board, or turn off NCQ to maintain data integrity.  

 

by: meyersdPosted on 2009-09-15 at 00:56:32ID: 25332700

Greaaaaaaaaaaaaaat. Just what we need. I see what you mean about the Google results.

You're talking specifically SATA II NCQ, yes?

 

by: dlethePosted on 2009-09-15 at 01:01:48ID: 25332729

That is the only kind of NCQ that there is.  SCSI uses a term called TCQ, which is similar, but not exactly the same.

 

by: meyersdPosted on 2009-09-15 at 01:45:06ID: 25332959

Oh, s@#$! You're right. I've been referring to TCQ as NCQ for yonks without realising my error.

You learn something every day.

 

by: zacker69Posted on 2009-09-15 at 05:36:25ID: 25334147

Thank you ! that help me. So I will no turn NCQ on. FYI, I use Windows XP  with Promise TX4310 SATA board and Seagate Harddsik  that support NCQ. Thank you dlethe! You probably prevent me to have some data lost!

 

by: gikkelPosted on 2009-09-15 at 17:10:15ID: 25340772

You shouldn't run into any problems enabling NCQ with your controller...yes, there were some issues with Nvidia controllers, but they've, for the most part, been identified (along with many other nvidia controller issues).  You're more likely running into data corruption issues just by enabling raid than you would by turning on NCQ.  I've had NCQ enabled for quite some time on many different platforms and have yet to see data corruption issues...and in case there are, you should always have a current backup!  :)

20120131-EE-VQP-002

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