Date: Mon, 17 Mar 2003 20:32:17 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Jeff Roberson <jroberson@chesapeake.net> Cc: Brooks Davis <brooks@one-eyed-alien.net>, Julian Elischer <julian@elischer.org>, Alfred Perlstein <bright@mu.org>, FreeBSD current users <current@FreeBSD.ORG>, fs@FreeBSD.ORG Subject: Re: Anyone working on fsck? Message-ID: <3E76A151.320A1E12@mindspring.com> References: <20030317230147.I66343-100000@mail.chesapeake.net>
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Jeff Roberson wrote: > On Mon, 17 Mar 2003, Terry Lambert wrote: > > Jeff Roberson wrote: > > > On Mon, 17 Mar 2003, Brooks Davis wrote: > > > > I am still intrested in improvements to fsck since I'm planning to buy > > > > several systems with two 1.4TB IDE RAID5 arrays in them soon. > > > > > > For these types of systems doing a block caching layer with a prefetch > > > that understands how many spindles there are would be a huge benefit. > > > > I call that layer "Vinum" or "RAIDFrame", since that's a job I > > expect that code to do for me. 8-). > > They are not responsible for data caching. Only informing the upper > layers how many spindles they have. Software RAID should be a transform > only in my opinion. There is no reason to have duplicate block caches in > system memory. Let's turn that around: "There is no reason to have duplicate spindle knowledge". Actually, I was not suggesting duplicate block caches, I was suggesting cache attribution by spindle by the code that knows what block lives on what spindle. Even so, for RAID, this is generally problematic, because there's multiple locations for the block: where it lives, where it's mirrored, where it's parity block lives, etc.. Ideally, these are all different spindles, so the problem can't be fixed by a simple cache. 8-(. You would need a chain of spindle references, supplied by the code that knows the spindle, hung off the cache object. Gets ugly fast. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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