funsec mailing list archives
Re: Database design.
From: Drsolly <drsollyp () drsolly com>
Date: Tue, 6 Jun 2006 22:24:33 +0100 (BST)
On Tue, 6 Jun 2006 Valdis.Kletnieks () vt edu wrote:
On Tue, 06 Jun 2006 21:49:18 BST, Drsolly said:300 gb drives cost about $100. You can put four of those in one computer, total cost maybe $600. For 460 terabytes, you'd need some 400 of those, which would cost $240,000.Yeah, and that DMX3 quote would have been a lot cheaper if they'd just used cheap $100 ATA drives, instead of the drives they actually use. However, when you're looking at 300 terabytes of disk, if you're using drives with a 3-year MTBF like they use in the average consumer desktop, you're looking
I'm not sure that the MTBF is 3 years. The guarantee on these things is 3 years. If they're expecting half of the drives they sell, to become warranty replacements, then they did their sums wrong. I suspect that the MTBF is a lot more than 3 years (and that's borne out by my experience with them). I checked. The mtbf for these drives (according to Maxtor), is 1.2 million hours = 137 years.
at a failure *EVERY DAY* on the average. Now the fun - even if you have a
So if you have 1000 drives, the mtbf would be around 1200 hours. One drive failure every seven weeks.
hot spare that the array can rebuild onto, what is the probability that (a) you'll have another drive fail before the rebuild finishes and (b) that the 2nd failure is inside the rebuilding RAID set?
That's not how I'd do it - I'd have three servers running in parallel. If one fails, you replace it while the other two are still running. Also, for a national database system like this, you'd have the database replicated in more than one site, to allow for the possibility of an outage at one site.
Hmmm.. let's see. A petabyte would be about 3,000 drives, and a failure every 8 hours. Assuming you create 100 RAID sets of 30 drives each, and you can rebuild a 30-drive RAID in 24 hours, you're looking at permanently trashing a RAID set on the order of once or twice a year.... (You can improve your chances by creating more RAID sets - but then you need to allocate more hot spares....)
I suggest you redo your calculation with the correct mtbf of 1.2 million hours. _______________________________________________ Fun and Misc security discussion for OT posts. https://linuxbox.org/cgi-bin/mailman/listinfo/funsec Note: funsec is a public and open mailing list.
Current thread:
- RE: Database design., (continued)
- RE: Database design. Blanchard_Michael (Jun 06)
- Re: Database design. Valdis . Kletnieks (Jun 06)
- Re: Database design. Mike Owen (Jun 06)
- Re: Database design. Brian Loe (Jun 06)
- Re: Database design. Drsolly (Jun 06)
- Re: Database design. Dude VanWinkle (Jun 06)
- Re: Database design. Drsolly (Jun 06)
- Re: Database design. Dude VanWinkle (Jun 06)
- Re: Database design. Drsolly (Jun 06)
- Re: Database design. Valdis . Kletnieks (Jun 06)
- Re: Database design. Drsolly (Jun 06)
- Re: Database design. Valdis . Kletnieks (Jun 06)
- Re: Database design. Drsolly (Jun 06)
- Re: Database design. Blue Boar (Jun 06)
- Re: Database design. Drsolly (Jun 06)
- Re: Database design. Blue Boar (Jun 06)
- Re: Database design. Drsolly (Jun 06)
- Re: Database design. Valdis . Kletnieks (Jun 06)
- Re: Database design. Brian Loe (Jun 07)
- Re: Database design. Blue Boar (Jun 06)
- Re: Database design. Drsolly (Jun 06)