Date: Fri, 24 Apr 2009 02:45:29 -0400 From: Scott Burns <scott@bqinternet.com> To: Alexander Kabaev <kabaev@gmail.com> Cc: freebsd-fs@freebsd.org Subject: Re: UFS2 metadata checksums Message-ID: <49F16009.3080206@bqinternet.com> In-Reply-To: <20090423195335.521db0a7@kan.dnsalias.net> References: <49F048FB.6000401@bqinternet.com> <20090423195335.521db0a7@kan.dnsalias.net>
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Alexander Kabaev wrote: > On Thu, 23 Apr 2009 06:54:51 -0400 > Scott Burns <scott@bqinternet.com> wrote: > >> Hi guys, >> >> I have spent some time writing a kernel module which calculates a >> checksum of a UFS2 dinode structure and stores it in the reserved >> space of the inode when writing it to disk. It is then verified when >> the inode is read from disk. If the checksum verification fails, the >> read returns an error (currently EIO). >> >> I believe that protecting metadata integrity is important, especially >> as storage capacity grows. Bitrot is a fact of life, and bad things >> can happen if the kernel acts on a corrupted inode. Not only does >> this module improve the stability of a server, but it also helps to >> prevent additional damage to the filesystem that can be caused by >> metadata corruption. >> >> I'm aware that data integrity issues are addressed with ZFS, but >> unfortunately ZFS is still not yet suitable for many workloads. I'm >> also aware that integrity checking can be done by using GELI between >> the filesystem and the disk, but at a noticeable cost in performance >> and space utilization. The method this module uses is fast and does >> not use any additional space. Most importantly, it builds on mature >> code that has worked well for decades. >> >> Before I spend much more time on it, I have some questions: >> >> 1) Has anyone else done any work in this area? >> >> 2) Is there a demand for this in FreeBSD? >> > > This is actually something I would love to have in the base system, > but inodes are not the only structures that need the integrity > protection. Pretty much every other metadata block, from cylinder group > blocks to indirect blocks for files need similar protection for > this to be of real use. > > -- > Alexander Kabaev As long as there is some interest in this kind of functionality, I will continue working on it. The next step is to protect metadata structures beyond inodes. I am hoping to have some results to post in the next few weeks. -- Scott Burns System Administrator BQ Internet Corporation
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