On Friday 22 of April 2011 10:03:52 Bakul Shah wrote: > On Thu, 21 Apr 2011 18:41:25 EDT erik quanstrom <quans...@labs.coraid.com> wrote: > > > IIRC companies such as Panasas separate file names and other > > > metadata from file storage. One way to get a single FS > > > namespace that spans multiple disks or nodes for increasing > > > data redundancy, file size beyond the largest disk size, > > > throughput (and yes, complexity). > > > > that certainly does seem like the hard way to do things. > > why should the structure of the data depend on where it's > > located? certainly ken's fs doesn't change the format of > > the worm if you concatinate several devices for the worm > > or use just one. > > ? > > It all boils down to having to cope with individual units' > limits and failures. > > If a file needs to be larger than the capacity of the largest > disk, you stripe data across multiple disks. To handle disk > failures you use mirroring or parity across multiple disks. > To increase performance beyond what a single controller can > do, you add multiple disk controllers. When you want higher > capacity and throughput than is possible on a single node, you > use a set of nodes, and stripe data across them. To handle a > single node failure you mirror data across multiple nodes. To > support increased lookups & metadata operations, you separate > metadata storage & nodes from file storage & nodes as lookups > + metadata have a different access pattern from file data > access. To handle more concurrent access you add more net > bandwidth and balance it across nodes.
<![RANT[ except those are not 100% orthogonal. not in theory, and even less in implementations. you risk ending up with big-ball-of-mud code, or abstracting all your performance (and flexibility and metadata like S.M.A.R.T.) away. also, (almost every) network hop and node lessens the compound reliability; some even introduce entirely new failure modes. ]]> so kudos to Isilon for actually having build great stuff :) -- dexen deVries [[[↓][→]]] ``In other news, STFU and hack.'' mahmud, in response to Erann Gat's ``How I lost my faith in Lisp'' http://news.ycombinator.com/item?id=2308816
