Date: Fri, 23 Nov 2007 14:45:37 +0100 From: "Christian Walther" <cptsalek@gmail.com> To: "Jan Catrysse" <j.catrysse@proximedia.be> Cc: freebsd-questions@freebsd.org, Bill Moran <wmoran@potentialtech.com> Subject: Re: RAID1 synchronisation - howto OR not necessary? Message-ID: <14989d6e0711230545k4b32c55bs3564647043f9f4ed@mail.gmail.com> In-Reply-To: <20071123092146.E0E1B2878E@smtp.proximedia.com> References: <20071122155640.fa7e0536.wmoran@potentialtech.com> <20071123092146.E0E1B2878E@smtp.proximedia.com>
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Hi, On 23/11/2007, Jan Catrysse <j.catrysse@proximedia.be> wrote: > > From: Bill Moran [mailto:wmoran@potentialtech.com] > > Sent: Thursday, November 22, 2007 9:57 PM > > To: Jan Catrysse > > Cc: freebsd-questions@freebsd.org > > Subject: Re: RAID1 synchronisation - howto OR not necessary? > > > > "Jan Catrysse" <J.Catrysse@proximedia.be> wrote: > > > [...] > This is what I found in a 3Ware manual: > Verification can provide early warning of a disk drive problem or failure. [...] Yes, it deals with drives failing silently. It's possible that data on a disk can get corrupted. You don't see the error until you read the block the next time. AFAIK the data contained in the bad block is delivered to the CPU/RAM and can cause some damage there. The problem I see with this setup is that you can't know which block is the one that is okay. You need some additional feature like a checksum for each block to check which one is correct. This isn't supported by all file systems, so you can only see that there is a difference between two blocks which sould normally be identical. I doubt that cheep RAID-Controllers have this capability, so you have to stick to some software solution. Does FreeBSD take care about something like this, I mean for software RAIDs? Regards Christian
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