On Mon, 28 Nov 2011 20:06:35 +0000 wilsonjonathan <piercing_male@xxxxxxxxxxx> wrote: > Quick question regarding linear raid. > > If a disk fails on a linear raid I understand how the raid is > non-recoverable, as a whole, as it has lost a chunk of data. > > However is it possible to recover the data from the non-failed portion > of the raid as I assume linear works by starting at one end of the array > and slowly progresses to the other? > > Or perhaps it is dependent on the file system on the array, eg. ext > works by trying to place files distant to each other to help reduce the > possibility of fragmentation? > > Perhaps the filesystem meta data, or some portion, may span between two > physical drives which would corrupt its table? > > And obviously if a file spans two disks it would be missing part of its > data? Yes. > > Does the raid underlying a file system do its own things, re-space, > physical data layout, etc; or does/can a file system impact on the > workings of an array? It is entirely up to the filesystem. The RAID just catenates the spaces together into one big space. The filesystem decides where in that space to put all the different things it wants to write. If you loose one drive from a linear array then recovery would be very difficult and have no guarantees. > > The more I look into software raid the more fasinated I become with it > and its inner workings. While its way beyond me in some of the maths and > the fact I am un-proficient in C it has really caught my intrigue, and > all because I wanted to set up a small home server ;-) > That's just the beginning -- before you know it you will be studying the maths and learning more C - you won't be able to help yourself! NeilBrown
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