Messages in this thread |  | | | Subject | Re: Filesystem optimization.. | | From | "Michael O'Reilly" <> | | Date | 30 Dec 1997 12:02:48 +0800 |
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hans@grumbeer.inka.de (Hans-Joachim Baader) writes:
> In article <x74t3szrih.fsf@metal.iinet.net.au> you write: > >While staring dejectedly at a filesystem holding a tad of 3 million > >files, and looking at the 'orrible latency to open a file, it occured > >to me that with most usage patterns, two things are true: > > How many of these files are actually accessed within an our? Or within > a day?
About 100,000 per hour. There is some cache locality, but not much. (The machine is running with around 300meg of ram as a disk cache, and stays disk bound for about 60 - 70% of the time).
> > > > 1) There are very few inodes that have more than one parent > > (i.e. more than one filename pointing to them) > > No, a news spool of INN actually contains many hard links.
True, but a news spool is a very unusual file system anyway.
> > 3) On most modern hard disks, the cost of reading 4K as > > opposed to reading 1K is minute (it's dominated by > > seek times etc). > > It could actually speed up access. But I think prefetching is > done already anyway, at various levels. > > >Then it occured to me that if you force aligning inodes on 64 byte > >boundries, the addressable filesystem goes to 256gig (probably enough > >for now). > > No. Terabyte disk arrays already exist, and terabyte disks and files > will be there within a few years. If we ignore this we end up with > a degenerate system like Windoze.
It doesn't limit the size of the filesystem, just requires that the inodes lie in the first 1/4 terabyte or first 1/2 terabyte. Not exactly a terrible restriction. :)
> >Comments?? (people dying to implement such a beast? :) > > I guess something should be done, but not this way. There are > several new filesystems under construction. Perhaps one of these > can implement some optimizations.
There are indeed a number under development, but I was more looking for something that would be useable in the short term.
Ext2 is a nice fast filesystem. This is a relatively small change that would hopefully make it faster yet, without noticeable cost.
Michael.
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