On Thu, 29 Mar 2007 at 12:13pm, John R Pierce wrote > chrism at imntv.com wrote: >> Joshua Baker-LePain wrote: >>> >>> You know, the whole "disk is cheap, so why use RAID5?" argument just >>> doesn't wash with me. Sure, disk *is* cheap. But some of us need every >>> GB we can get for our money (well, given I'm spending grant money, it's >>> actually *your* money too (if you live in the US)). >>> >>> To demonstrate, let's look at a 24 drive system (3ware has a 24 port 9650 >>> board). Newegg has 500GB WD RE2 drives for $160. So for $3840 in drives >>> I can get: >>> >>> a) 6TB RAID10 => $0.64/GB >>> >>> or >>> >>> b) 10.5TB RAID6 w/ hot spare => $0.37/GB >>> >>> Umm, I'll take 75% more space for the same money, TYVM. >>> > > did those prices factor in the drive bay infrastructure for 24 drives with > cabling, redundant power supplies, etc? Given 3840=160*24, no. ;) But those prices would be the same however you configure the drives. > btw, I would NOT build a 20-something raid5/6 set. the rebuild times would > be massively slow, opening a large window for double drive failure. > Before you say 'nah, would never happen', check out phpbb.com, they lost > their web server and forums to a double failure last month, and yes, they had > a hotspare so the rebuild started immediately. > > The large SAN vendors usually don't recommend building raid5 sets larger than > 6-8 disks, and will stripe or concatenate multiple of those on the typical > SAN with 100s of spindles. Myself, I'll stick with RAID10 for anything > critical. Would that I had the money to and still get the space I need. Even doing 2 12 disk RAID6 sets (each with a hot spare) gets you 9TB which is 50% more space for the same money as RAID10. To try to cut this debate short (hah!), this all boils down to a simple CBA. For me, I need massive amounts of fairly reliable, fairly fast space at as good a price as I can manage. RAID5/6 on systems backed up to tape (oops, I seem to be crossing threads) fulfills those requirements. For me. YMMV. No guarantees. Offer not valid in NV or NY. Do not taunt Happy Fun Ball(TM). -- Joshua Baker-LePain Department of Biomedical Engineering Duke University