Converting a WD drive or Seagate drive for RAID use

Hello all. Sorry if I am going to be alittle long winded here, but I have alittle of a dilema that I'm trying to advert and I want to give as many details as possible. I am beginning to experiment with Cisco Callmanagers and such and have procured a Dell 1950 server with four 2.5" drive bays. It will accept either SAS drives or SATA.

The 1950 uses hot swap caddys and there is going to be alot of data stored on this thing. So I figured if I installed four 500 GB drives in RAID 5 that would give me about 1.5 TB of storage for the Callmanager and a bunch of other things I wanted to use the box for. I've done some research on this box and have found that there are a couple of problems that I'm likely to run into.

The box had all it's drives removed prior to me purchasing it (company policy) so I plan on using higher end consumer drives like the WD Scorpio Black or the Seagate Momentus drives in it. Per Dell system specs and recommendations, consumer drives are not supported in the box being they are not rated blah blah blah. They state I should just purchase Enterprise grade drives like the WD RE drives or a Seagate Constallation, but I would spend a months mortage to purchase those types of drives in the quantity and size needed. Obviously that's not happening.

One of the main reasons you shouldn't run the consumer drives in a RAID configuration is due to the way the drive's error recovery control is configured on the drive's firmware. Long story short the drive should be configured to let the RAID controller do the majority the determining of if there is a read/write failure on the drive not the drive itself and for the drive to timeout and give the RAID controller control. Consumer drives don't do this by default.

I know there used to be a utility called WDTLER that you could use on WD consumer drives and make them coexist in a RAID array nicely, but WD has since removed that ability in the newer firmwares. Seagate consumer drives also run error recovery controll, but there is no program that I have found that can tweek it.

So I guess here is the root of the question. Does anybody have/know of a utility that can modify a drive and make it truely RAID 5 compliant. I'm a Seagate fan, but I don't hate on WD either. I've been in the game for a long long time. Basically back when 30 MB was a huge HDD and floppy drives were,,,, well floppy. So I've seen all brands of HDDs fail, so I'm not so partial that I won't consider other brands. Basically whom ever has the utility to accomplish what I desire is gonna earn my business. Again I know it's a long post. Thanks for the help guys.

TDLR issues mostly pop up on 5400RPM drives (espeically the WD Caviar Greens). On 7200RPM drives, I haven't heard the issue occurring as much.

A LOT of people here prefer Hitachi drives for RAID arrays however. I personally haven't run one, so I'm not sure why, but it's the most popular (WD Blacks seem to be the next popular, however).

Knufire said:

TDLR issues mostly pop up on 5400RPM drives (espeically the WD Caviar Greens). On 7200RPM drives, I haven't heard the issue occurring as much.

A LOT of people here prefer Hitachi drives for RAID arrays however. I personally haven't run one, so I'm not sure why, but it's the most popular (WD Blacks seem to be the next popular, however).

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Why Hitachi? I haven't turned anything up, but is there a reason other than they are fairly cheap?

To my knowledge, no one has been able to modify a HDD bios to enable TLER/CCTL/LCC/whatever to use the drive in a RAID setup safely. As you said yourself, the feature used to be there and the user was able to disable and enable TLER on WD drives, but of course, WD removed it completely from its non-RAID enabled drives. Unless the drive supports the feature, you can't enable it.

That being said, as Knufire also stated, most of the higher end drives usually fair ok in a RAID environment. Personally, I attribute that to the fact (that I have experienced with my own drives), that the Green (5400rpm) drives cause issues in a RAID setup for two reasons:

1. The RAID controller might view a Green drive that is taking too long to spin back up (for example, it *just* spun down after being idle and now has to spin back up after a read/write request from the controller), as a non-responsive drive and drop it from the array, breaking the RAID array.

2. Nearly every Green drive I have owned, has at some point developed a problem sector(s). Sectors which cannot be read, and need to be re-read over and over again (this is the Error Recovery Process), could take too long, also causing the RAID controller to think the drive has gone bad and drop it from the array, which once again, will break a RAID array.

TLER is Time Limited Error Recovery. Basically, this feature allows a drive to go completely unresponsive while it tries to correct a read error. Most of the time, these read errors are corrected in a few revolutions of the disk and no decrease in performance is noticed. Read errors that take a long time are allowed to go an extremely long time before reporting a read error to the disk controller. TLER is set to 90 seconds on all WD Green, Blue, and Black drives -- so don't use any of these in RAID. The "RE" line has TLER limited to 7 seconds. Most RAID controllers will only wait around 8-10 seconds for a disk to respond, so if it exceeds that time trying to recover from a read error, the controller drops it from the array as "failed", which puts the array in a degraded state. As of a few years ago, these options are not changeable on any disk, even with the TLER utility.

Other green features aren't as much of a problem, such as head parking or spinning the disk down. Most of these features can be controlled through the operating system to prevent issues.

kossuth said:

Why Hitachi? I haven't turned anything up, but is there a reason other than they are fairly cheap?

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We prefer Hitachi drives because they don't have TLER or other "Green Features" that can cause the RAID array to become degraded or break. I'm running 25 raw terabytes of spinning Hitachi disk in my server (7x 1tb, 9x 2tb) and they have given me no trouble.

Didn't WD buy out Hitachi's hard drive line last year? Any idea how this has affected Hitachi drives being produced now?

Yes and I have no idea. I hope they don't ruin the line, but they probably will.