On Wed, Dec 17, 2008 at 9:09 AM, Johan Hartzenberg <jhart...@gmail.com>wrote:
> > On Wed, Dec 17, 2008 at 2:46 PM, Thanos McAtos <mca...@ics.forth.gr>wrote: > >> >> >> My problems are 2: >> >> 1) I don't know how to properly age a file-system. As already said, I need >> traces of a decade's workload to properly do this, and to the best of my >> knowledge there is no easy way to do this automatically. >> >> 2) I know very little of ZFS. To be honest, I have no idea what to expect. >> Maybe I'm doing aging the wrong way or ZFS suffers from aging when is has to >> allocate blocks for writes/updates and not on recovery. >> >> I would expect the fill level of the pool to be a much bigger factor than > the "age" of the file system. However an old but very empty file system may > have its data blocks spread far apart (large gaps in between). So a "new" > empty file system may have all its allocated data blocks at the start of a > disk, and a "old" empty file system may be scattered all over the disk. > However, since we are talking about more space than data, and ZFS only > "rebuilds" the blocks which are in use, this is a special case and while the > difference my be relatively large, it will likely be small real difference. > > But I am speculating. The CoW nature of ZFS will probably make it very > hard to consistently create a "fragmented" file system!!! > > -- > Any sufficiently advanced technology is indistinguishable from magic. > Arthur C. Clarke > > My blog: http://initialprogramload.blogspot.com > I would expect there to be some sort of clean-up process that either runs automatically or that could be scheduled to optimize block layout on a regular basis to avoid just such an issue. --Tim
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