On 02/15/16 16:02, Karel Gardas wrote: >> ..And therefore you need enterprise disks because they behave "cleanly", as >> when using those only, essentially full softraid QoS is maintained at all >> times. > > Interesting! I've understand Nick excellent email in completely > reversed sense. I understood it in "use consumer drives which fail > really slowly and with degraded performance which will give you a > chance to notice it at all. With enterprise, your drives may fail too > quickly so there is a danger of failing drive in a array which is just > rebuilding after another drive failure few hours ago". >
And that's the way I meant it... I've had maybe five drives do the "slow-fail" thing. Maybe. In 34 years, including selling and supporting thousands of computers at a very successful store, working for a few very large companies, and working with a lot of tiny companies. I'd file that under "it happens, don't wait up, and certainly don't design around it". In contrast, the number of "fast failures" I've seen on "Enterprise grade" stuff is ... stunning. And, I think I've seen evidence of one "event" taking multiple drives off-line at once, with predictable results to the array. Fix? Remove and re-insert drive, and rebuild, since there is really nothing wrong with the disk 80-90% of the time. Oh, guess you need a hot-swap enclosure, then. My experience can be summed up as: Simple systems have simple problems. "Enterprise Grade" stuff that is never supposed to break or go down...will (due to complexity) and will stay that way for amazing periods of time (due to your lack of preparation, because you don't believe it will happen). And when it comes to disk systems, IF "enterprise grade" *disks* are any better (and I don't believe it), when combined with enterprise grade enclosures and enterprise grade disk controllers and firmware and fancy drivers...no question in my mind, consumer grade SATA disks on dull interfaces win, hands down. Remember, it isn't WHY you lost data that matters (be it hardware, software or human error), just that you did. (A common failure part in "enterprise grade" servers is the disk backplane board. There's almost no active electronics on it, but they fail often. they don't exist on a desktop pc. I suspect the vibration of drives cracks the solder joints). with My recommendation: 1) Plan for things to break. 2) Plan for ANYTHING to break. 3) Have an in-house way of dealing with whatever breaks. 4) Don't rely on others. It's not their business that is down. 5) The people you paid to bail you out of 1 & 2 so you don't have to worry about 3 and 4 WILL let you down and will not live up to their promises, and when you read the fine print, you will realize there isn't a damn thing you can do about it, 'cept pay them again when the contract comes up. And after you do that, you will realize that obsessing over "enterprise grade" parts is not part of the design. NOTE WELL: That's my opinion based on *my* experience (including what was almost a "controlled experiment" along those lines). Every manufacturer out there says I'm wrong. Most of my coworkers say I'm wrong. Every new technology (like SSDs) give another opportunity to "change everything" (and the results always seem to be the same, but maybe THIS time will be different). If you follow my advice and things blow up, you will look like an idiot, and I really don't want to hear about it. If you follow the mainstream mindset, you can always say, "That's what (almost) everyone said is the right way, not my fault!". Blindly following the opinions of some crackpot on the internet may be foolish. Blindly following the opinions of people who profit from what they advise you will be expensive. Nick.
