aha, now i see what you're saying -- yeah i have no evidence either way as to what happens in a long self-test in that regard. -dean On Sat, 7 Aug 2004, Salyzyn, Mark wrote: > As long as the relocation contains the original information; which is > only the case if the relocation is done on a write to the disk. > > A RAID-5 generated relocation allows the data to be reconstructed on a > media failure on erad, and the relocation (triggered by a re-write) > would contain the correct information preventing corruption. > > Sincerely -- Mark Salyzyn > > -----Original Message----- > From: dean gaudet [mailto:dean-list-linux-raid@xxxxxxxxxx] > Sent: Saturday, August 07, 2004 4:13 PM > To: Salyzyn, Mark > Cc: Kanoa Withington; Derek Listmail Acct; linux-raid@xxxxxxxxxxxxxxx > Subject: RE: Scrub? > > no, that's not how it works. i'm referring to the hard disk itself > relocating a sector -- it's transparent to the host/raid. the only > thing > the raid software might see is that the disk will be less snappy while > it's running the SMART long test. (mind you i do this on live busy > systems and i don't really tend to notice it -- although on particularly > busy weeks, some disks can take several days to complete their self test > in the few spare cycles they find.) > > -dean > > On Sat, 7 Aug 2004, Salyzyn, Mark wrote: > > > Problem with running the relocation is that the RAID-5 will now be > > corrupt. The RAID-5 algorithm needs to be in-touch with disk block > > relocation so that it can correct the parity and the data. > > > > Sincerely -- Mark Salyzyn > > > > -----Original Message----- > > From: dean gaudet [mailto:dean-list-linux-raid@xxxxxxxxxx] > > Sent: Friday, August 06, 2004 5:59 PM > > To: Kanoa Withington > > Cc: Salyzyn, Mark; Derek Listmail Acct; linux-raid@xxxxxxxxxxxxxxx > > Subject: RE: Scrub? > > > > On Fri, 6 Aug 2004, Kanoa Withington wrote: > > > > > On Fri, 6 Aug 2004, Salyzyn, Mark wrote: > > > > Just reading the entire array should correct the bad blocks, so > > reverse > > > > the sense of the dd: > > > > > > > > dd if=/dev/md0 of=/dev/null bs=200b > > > > > > > > to find and replace the bad blocks (making the assumption that md > > works > > > > like the H/W RAID cards). > > > > > > In this case software RAID does not work like the H/W cards. Finding > > > an unreadable block that way in a software array would cause it to > go > > > into a degraded state. > > > > if the disks support SMART (i.e. they're less than a few years old) > then > > try running the smart long selftest... it can be done online and on > many > > disks it will force sector reallocation (and produce a SMART log event > > so > > you know it happenned). > > > > get smartmontools and run "smartctl -a" to see info on your drive, and > > "smartctl -t long" to launch the long test. man page has more > examples. > > > > i run smart long tests on each my disks once a week (staggerred over > > many > > nights)... see /etc/smartd.conf. > > > > -dean > > > - > 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
