On Sat, Mar 6, 2010 at 5:02 PM, Mark Knecht <markknecht@xxxxxxxxx> wrote: > First post. I've never used RAID but am thinking about it and looking > for newbie-level info. Thanks in advance. > > I'm thinking about building a machine for long term number crunching > of stock market data. Highest end processor I can get, 16GB and at > least reasonably fast drives. I've not done RAID before and don't know > how to choose one RAID type over another for this sort of workload. > All I know is I want the machine to run 24/7 computing 100% of the > time and be reliable at least in the sense of not losing data if 1 > drive or possibly 2 go down. > > If a drive does go down I'm not overly worried about down time. I'll > stock a couple of spares when I build the machine and power the box > back up within an hour or two. > > What RAID type do I choose and why? > > Do I need a 5 physical drive RAID array to meet these requirements? > Assume 1TB+ drives all around. > > How critical is it going forward with Linux RAID solutions to be able > to get exactly the same drives in the future? 1TB today is 4TB a year > from now, etc. > > With an 8 core processor (high-end Intel Core i7 probably) do I need > to worry much about CPU usage doing RAID? I suspect not and I don't > really want to get into hardware RAID controllers unless critically > necessary which I suspect it isn't. > > Anyway, if there's a document around somewhere that helps a newbie > like me I'd sure appreciate finding out about it. > > Thanks, > Mark I'm not sure about a newbie doc, but here's some basics: You haven't said what kind of i/o rates you expect, nor how much storage you need. At a minimum I would build a 3-disk raid 6. raid 6 does a lot of i/o which may be a problem. Raid-5 is out of favor for me due to issues people are seeing with discrete bad sectors with the remaining drives after you have a drive failure. raid-6 tolerates those much better. Even raid 10 is not as robust as raid 6 and with the current generation drives robustness in the raid solution is more important than ever. But raid 6 uses 2 parity drives, so you'll only get 1TB of useable space from a 3-disk raid 6 made from 1TB drives. mdraid just requires replacement disks be bigger than the old disk you're replacing. You might consider layering LVM on top of mdraid to help you manage the array as it grows. Greg -- Greg Freemyer Head of EDD Tape Extraction and Processing team Litigation Triage Solutions Specialist http://www.linkedin.com/in/gregfreemyer Preservation and Forensic processing of Exchange Repositories White Paper - <http://www.norcrossgroup.com/forms/whitepapers/tng_whitepaper_fpe.html> The Norcross Group The Intersection of Evidence & Technology http://www.norcrossgroup.com -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
