Can you stop sending me double copies of every mail please Chris? Do you know what REPLY-TO means in the headers?
On Mar 9, 2011, at 1:56 PM, Chris Murphy wrote: > Chad, I am aware of the magnitude of the problem *IF* corruption occurs in > RAID 5. That is not even remotely relevant with a conversation about the > probability of such corruption. > > There appear to be two competing claims here: > > 1. RAID 5 itself is well known for having silent data corruption and should > not be used. > > 2. Apple sold, until very recently a Mac OS X based, hardware RAID 5 > solution, supposedly honoring a "do no evil, cause not harm" philosophy. > > RAID 5 is not a new thing. Silent data corruption is not a new thing. I won't > buy an argument suggesting Apple just figured this out recently and that's > one of the reasons why they killed the Xserve RAID. > > Chris Murphy > > On Mar 9, 2011, at 1:51 PM, objectwerks inc wrote: > >> >> On Mar 9, 2011, at 1:46 PM, Chris Murphy wrote: >> >>> >>> >>> On Mar 9, 2011, at 1:35 PM, objectwerks inc wrote: >>> >>>>>> The integrity of the data with files after any issues such as these may >>>>>> be suspect, especially if the fileystem was on a RAID5 which is very >>>>>> well known for silent data corruption. This is why RAID5 should not be >>>>>> used. >>>>> >>>>> OK that's possibly a whole separate thread for qualifying such a >>>>> statement. Apple has a supported product that uses RAID 5. I have clients >>>>> with them and they've lost drives, and no data, and no data corruption. >>>>> And an even larger sample size exists if filesystems other than jhfs+ are >>>>> considered. RAID 5/6 are common with ext3, ext4, XFS and other file >>>>> systems without anyone suggesting RAID 5 in particular is known for >>>>> itself increasing the incidence of silent data corruption. >>>>> >>>> >>>> >>>> There is a reason why it is called silent data corruption. They may not >>>> know they have it. It happens all the time and with HW raid 5 you may not >>>> even know it for a long time. >>>> >>>> This is the whole reason why ZFS was made. >>> >>> ZFS was not made for combating this claim of RAID 5 specific silent data >>> corruption, but rather silent data corruption in general. >> >> And the difference is? You corrupt one disk in a RAID 5 array and the >> whole array is corrupted. >> >>> >>> RAID 5 employs parity. RAID 1 does not, nor do conventional non-arrayed >>> jhfs+ volumes. While RAID parity is not as sophisticated at ZFS >>> checksumming, it is certainly better than nothing. So there is some error >>> detection and correction possible, so I'm not understanding how RAID 5 is >>> "well known for silent data corruption" and should not be used. I think >>> this is a rather remarkable claim. >>> >>> >>> Chris Murphy >> >> >> If you have one disk that has silent data corruption (and parity may not >> help you at all as you calculate your new parity on the corrupted data) you >> compound it with RAID 5. >> >> http://www.raidinc.com/pdf/Silent%20Data%20Corruption%20Whitepaper.pdf >> >> >> http://boink.superatomic.com/2009/04/25/the-raid-5-write-hole/ >> >> >> http://www.google.com/#hl=en&sugexp=ldymls&xhr=t&q=raid+5+silent+data+corruption&cp=24&qe=cmFpZCA1IHNpbGVudCBjb3JydXB0aW9u&qesig=0VyEUZb1ePVXqTxPyJd8vg&pkc=AFgZ2tkTDI1HqM7fc6R1egXasC-1CNF3wT4BG5rzsZmDlr4IGBRuaMW3LWOqaaHzeI1IQlVZ2T5WTE3o3LlGRR6gLiYOy2lsHA&pf=p&sclient=psy&site=&source=hp&aq=0b&aqi=&aql=&oq=raid+5+silent+corruption&pbx=1&bav=on.2,or.&fp=ef34c9a9ed856910 >> >> >> > > _______________________________________________ > MacOSX-admin mailing list > [email protected] > http://www.omnigroup.com/mailman/listinfo/macosx-admin _______________________________________________ MacOSX-admin mailing list [email protected] http://www.omnigroup.com/mailman/listinfo/macosx-admin
