> -----Original Message----- > From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid- > owner@xxxxxxxxxxxxxxx] On Behalf Of Dan Stromberg > Sent: Friday, August 26, 2005 3:01 PM > To: Linux RAID > Cc: strombrg@xxxxxxxxxxxxxxx > Subject: number of global spares? > > > I've been working on a RAID setup with dual RAID controllers and > three expansion boxes - 48 disks in all, including data, parity and > global spares. > > We originally purchased the equipment expecting to get 16 terabytes of > usable space. > > Now that it's "all set up", we're really seeing more like 14 or 15 > terabytes, depending on how you do the calculation. > > Please be sure to use a fixed-pitch font when viewing the tables found > below. BTW, if people weren't so terrified of HTML, I could just make a > nice HTML table for easy reading without silly font requirements... > > Anyway, what we have right now is: > > global spares: 0,16,32,48 > > Raidset Disks used Data:parity ratio > 0 1,2,3,4,5,6,7,8,9,10 9:1 > 1 11,17,18,19,20,21,22,23,24,25 9:1 > 2 26,27,33,34,35,36,37,38,39,40 9:1 > 3 41,42,43,49,50,51,52,53,54,55 9:1 > 4 56,57,58,59 3:1 > > > And the vendor is suggesting that we move to something like: > > global spares: 0 > > Raidset Disks used Data:parity ratio > 0 1,2,3,4,5,6,7,8,9,10 9:1 > 1 11,17,18,19,20,21,22,23,24,25 9:1 > 2 26,27,33,34,35,36,37,38,39,40 9:1 > 3 41,42,43,49,50,51,52,53,54,55 9:1 > 4 56,57,58,59,16,32,48 3:1 > > ...or...: > > global spares: 0,16 > > Raidset Disks used Data:parity ratio > 0 1,2,3,4,5,6,7,8,9,10 9:1 > 1 11,17,18,19,20,21,22,23,24,25 9:1 > 2 26,27,33,34,35,36,37,38,39,40 9:1 > 3 41,42,43,49,50,51,52,53,54,55 9:1 > 4 56,57,58,59,32,48 3:1 > > > Does anyone have any comments on: > > 1) The sanity of these 10 disk RAID 5's? > > 2) The degree of loss of reliability incurred by moving 3 disks from > global spare to data? > > 3) The degree of loss of reliability incurred by moving 2 disks from > global spare to data? > > > To answer these questions, you probably need to know how the storage is to > be used. This single, large filesystem will be used by a variety of > researchers and students from around The University of California, Irvine, > but was purchased primarily by the Earth System Science part of the > Physical Sciences department, which in turn will primarily be storing many > approximately 100 megabyte files which comprise time series related to > climatology simulations. > > They don't feel that the storage has to be blazing fast, and 100% uptime > isn't paramount, however they very much do not want to lose their data. > > The filesystem will not be backed up - we simply don't have anything large > enough to back it up -to-, so if the some part of the storage solution > goes kerflooey, we're totally... er... out of luck, and they'll probably > be looking at me (the primary sysadmin on the storage configuration), > wondering why their data is gone. RAID5, 6 or 1 is not data backup! It is hardware redundancy!! Data loss or corruption can still occur with a RAID solution. RAID won't help if someone fat fingers a "rm" command. Corruption of the filesystem can also cause major data loss, without a failed disk. If the data was lost, what would it cost to re-create it? Enough to buy a backup system? Just my 3 cents! Guy > > Thanks! > > - > 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
