Thanks nanofrog for jumping back into the strand. Actually your statement quoted above does imply that the enterprise class hard drive with its 7 second limited error correction will, in terms of error correction, be worse than the desktop class hard drive for RAID 0.
NP.
RAID is complicated, and can get confusing rather quickly. Available online resources can be a bit too simplistic, and lead someone into trouble IMO.
At any rate, I get what you're meaning about the factory timings in the enterprise models.
But there's two aspects of information that're being missed (one is my fault
).
- You can change the timings on the enterprise disks (REx models).
- Even if you don't you won't see that issue like you would with consumer models (and why I forgot to mention #1 ). It has to do with the fact those disks are meant for the abuse RAID hands off to the disks via the additional sensors (i.e. if it senses the vibration is getting too high, it will act to prevent the heads from impacting the platter causing physical damage = bad sectors result).
I had studied the Wikipedia page on TLER and also a Samsung page on their
CCLR but don't understand the interactions of hard drive and controller, leading to my original question.
Understandable.
What's worse, the exact procedure/methods used internally in the disks are still somewhat proprietary (i.e. what sensor at what value will it temporarily disable the disk's operation in order to stabilize it). Yes, SATA is a specification (open standard), but what happens in the controller board's interaction with the platters, spindle motor, and stepper motor (operates the armature the heads are mounted to), can vary from drive maker to drive maker (though the basic process isn't that different between them). SATA has commands that can be sent bidirectionally (i.e. disk sends error message to the system). Think SMART data.
So long as a disk sends/receives data within the SATA IO specification, it's deemed compliant. What happens on the other side (disk controller), may fall under Intellectual Property = proprietary (Patents). Though there is a lot of commonality (basic requirements to operate the mechanics to get/transfer data), the way they do it may not be exactly the same. Same goes for platter production (density for example).
Yes RAID 0 is a bastard, and I'm afraid statements about RAID simpliciter sometimes overlook RAID 0 and become false. A writer of the Wiki page is obviously pissed that the utility WDTLER doesn't work on the newest WD drives, so TLER can't be disabled on their new enterprise drives. He/she writes:
"...having the choice of changing the TLER option gives the user the flexibility of purchasing the high performance drives that have TLER enabled and that are designed to run in a RAID array and using them as stand-alone single drives in their desktop computers and disabling the TLER option to enable better data recovery and lower chance of corruption and drive failures."
Here the writer carefully separates having "TLER enabled" from "designed to run in a RAID array" (durability which entails higher heat, noise, and cost) of the enterprise class drive. I think RAID 0 drives want TLER disabled for exactly the same reason that a stand-alone drive does. The writer goes on to slam WD with the conclusion:
"[New enterprise] RE disks are only suitable for RAID arrays and [new desktop] Caviar are only suitable for non-RAID use."
But here I think the first word "RAID" needs to be qualified "except RAID 0", and maybe the second word "RAID" too.
WD used to allow the TLER values to be adjusted in all of their disks (initially didn't have RE = RAID Edition disks for every niche, such as in the Green series). That's now changed, so only the RE series (RE4 to be a bit more specific) allow the TLER values to be adjusted by the user with the utility. The consumer models have had that ability removed. You can still do it with older drives, but no longer with anything new in this segment (standard Blue, Green or Black, or other specialty disks; anything not identified specifically REx in the model).
This has pissed some people off, but common sense should have led them to realize this "freebie" wouldn't last forever. They're after profits, and allowing this to continue on the consumer lines cut into that, as users weren't buying the RE models.
Some got burnt too, depending on what they were doing (i.e. using consumer models for a primary array).
Consumer GP disks were commonly used as primary (on-site) backups once the TLER values were adjusted, as they were suitable for that, and corporations are noticing power bills and HVAC requirements (especially during an upgrade to the existing facilities, new facilities, or a break down of existing equipment - it's expensive).
My purpose for joining drives in RAID 0 is for playback of some video which will stream at about 800 Mb/s (100 MB/s). A single drive can't read fast enough. Maybe two in RAID 0 can. Maybe three. If not three, I'll quit. Samsung 1 TB hard drives here cost 45% extra for enterprise class. That's fair, but if the 7 second error correction limit can't be disabled I'll go with desktop class. Backing up is fun to do.
2x disks will suffice for this, especially if the individual performance is at/over 100MB/s each (allows you to go past the 50% capacity mark). Think 2TB models that run at 7200rpm (greens aren't that fast).
With slower disks, it will still work, but you have to be mindful of the capacity, as data transfers slow down once you hit the inner tracks on the platters (same rotational speed, but shorter tracks = less data read/written per rotation = reduced throughput). Additional drives help with this, but it's also at additional cost.
In your case, you probably don't need to bother with enterprise grade disks (assuming you're using the SATA ports on the logic board, not a true RAID card), especially with a proper backup in place.
Yeah, it's a PITA to rebuild an array by hand off of backups, but it's an acceptable compromise to keep the costs as low as possible.
But the enterprise disks would reduce the statistics of this happening, and the values can be adjusted with the TLER Utility (not just disabled, but actually changed to other values). I know I've seen people complain this isn't possible, but it is. You just have to enter the correct command (values are contained within the command). No values, means defaults will be used.
Hope all of this helps.
