On Thu, 02 Nov 2006 22:03:05 -0800, Alexander Lind <[EMAIL PROTECTED]> wrote:
>> RAID, kiddo. >> It's more complex. It is something else that can go wrong. >> And...it DOES go wrong. Either believe me now, or wish you believed me >> later. Your call. I spent a lot of time profiting from people who >> ignored my advice. :) >> >Of course raid are more complex on a hardware level, but that doesn't >exactly make it more complex for _me_, the user, does it? > Alexander, Yes, it does. Not realizing the increased complexity and risks for the user just means you drank the koolaid and actually believe the marketing and advertising nonsense for hardware RAID products. If with *your* experience you really believe that hardware and firmware never have serious bugs or catastrophic failures, then you are statistically overdue for a number of unpleasant surprises. Here is an interesting question for you which may help you grasp the concept Nick is preaching; in the event of a nasty failure on a RAID where you absolutely *must* be able to recover the valuable data, do you stand a better chance of recovering the data from a hardware RAID configuration or a software RAID configuration? Though contrary to the marketing koolaid, the answer is software RAID. In a hardware RAID you are blindly trusting incompletely documented hardware and undisclosed firmware. You will *NEVER* have access to the firmware source code or the chip logic, so you never really know how it works exactly. In a software RAID configuration (ccd/raidframe/etc), you have the source code, know exactly how it works and the hardware is far less complex as well as reasonably well documented in most cases. With software RAID, at least you have a chance of mounting the raw disks and piecing thing back together manually. The odds of recovery are always better when things are simple and you actually know how they work. Mindlessly slapping a new disk into a hardware RAID after a disk failure only works *some* of the time and only for *some* types of failures. If you're not lucky enough to be in the *some* category, then you'll be dusting off those outdated backup tapes and updating your resume. Imagine telling your boss that there is no way to recover the data from the trashed RAID disks because the vendor refuses to release required hardware/firmware information. If you had kept things known and simple by using a software RAID, you may have had a chance of recovering the companys' financial records. Hardware RAID is fun, fast and useful for some applications but you should at least understand the additional complexity you're deploying, the additional risks caused by the complexity and the additional costs you will bear. When your only concern is reliability then your goal should be to keep it as simple as feasible. Less complexity and fewer unknowns not only means fewer things can go wrong but it also means a greater chance of recovery. Still not convinced? Let's say a bug is committed to the -CURRENT source tree in the driver for your hardware RAID card. Since reliability is so critical to you, you must have a completely identical hardware setup for constantly testing your hardware RAID controller with -CURRENT to prevent that bug from getting into a -RELEASE? Or maybe you went out and spent the few hundred bucks for an additional RAID controller like the one you use so you could donate it to one of the developers in the project who actually work on the driver? Nope, statistically you're probably a typical user who waits until release to see if your RAID volumes are hosed by an undiscovered bug. Luckily, with OpenBSD you have extremely dedicated expert developers covering up for your short-sightedness. The path of "Simple, Known and Tested" should be looking really good to you about now for reliability but if not, then there is really no point in arguing it any further. Not everyone can provoke Nick into yet another world class RAID RANT, but those who do darn well ought to learn something before he pulls out the nail gun again to show you what a worst case disk failure is really like. (no joke, search the archives). /JCR -- Free, Open Source CAD, CAM and EDA Tools http://www.DesignTools.org
