Date: Mon, 12 Oct 1998 20:18:53 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: francisco@natserv.com Cc: grog@lemis.com, freebsd-fs@FreeBSD.ORG Subject: Re: Optimizing space utilization Message-ID: <199810122018.NAA21730@usr07.primenet.com> In-Reply-To: <199810110304.XAA22392@federation.addy.com> from "Francisco Reyes" at Oct 10, 98 11:04:35 pm
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> >> On a 1 Gig partition by using 1/4 the number of inodes (sent -i 16384 > >> to newfs) I was able to save a little over 30MB. A 3% saving. :-) > >> I was still left with over 64K inodes, which I doubt I will use. > > > Interesting. At 262 bytes per inode, I'd only expect a saving of > > about 12 MB. Uh, what are you smoking? An inode is 128 bytes, exactly, including reserve space. Are you perhaps counting the mandatory 24 byte overhead on a directory entry, and assuming a 110 byte file name? If so, you should be aware that flexname allocations must round to 4 byte boundaries, so you are off by 2 (108 and 112 are evenly divisible by 4). > Something else I noticed.. > The total space reported by df (heading 1K-blocks) also went up > slightly. Don't recall exact number, but I think it was 3 to 5MB. Clearly, so long as we make a distinction between 512b physical blocks divided up between 4 inodes and 512b physical blocks that are agregated and represent portions of file system blocks, you can adjust the ratio of blocks used for inodes vs. blocks used for data. So yes, you could adjust this to get some space back. But if you go over an 85% fill, then even a perfect hash begins to have collisions. The historical 10% reserve was chosen as a compromise of diminishing returns for hash fill efficiency (read the FFS paper, and read Knuth's Seminumerical Algorithms). Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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