} -----Original Message----- } From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid- } owner@xxxxxxxxxxxxxxx] On Behalf Of Greg Freemyer } Sent: Saturday, March 06, 2010 5:33 PM } To: Mark Knecht } Cc: Linux-RAID } Subject: Re: What RAID type and why? } } 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. If he only needs 3 drives I would recommend RAID1. Can still loose 2 drives and you don't have the RAID6 I/O overhead. Also, you said your data is important. If so, you need a backup solution! 2 copies with 1 off-site. Maybe alternate between the 2 each day or week. How much data per day? How much data during the next 3 years? Guy } } 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 -- 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
