Date: Fri, 13 Aug 1999 18:53:06 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: Jos.Backus@nl.origin-it.com Cc: bde@zeta.org.au, phk@critter.freebsd.dk, vernick@bell-labs.com, freebsd-fs@FreeBSD.ORG Subject: Re: Help with understand file system performance Message-ID: <199908131853.LAA22289@usr09.primenet.com> In-Reply-To: <19990813152529.G12312@hal.mpn.cp.philips.com> from "Jos Backus" at Aug 13, 99 03:25:29 pm
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> On Fri, Aug 13, 1999 at 11:13:21PM +1000, Bruce Evans wrote: > [Poul-Henning wrote:] > > >Try fiddling the newfs parameters. I see 17% speedup using: > > > > > > newfs -b 16384 -f 4096 -c 100 > > Too bad tunefs doesn't have those options :-) These are not tunable options, they are initial layout options. > > ffs-4K-4K is only slightly faster than ffs-8K-1K now, presumably because > > drive caches are larger and command overheads are relatively higher (the KA > > acts like a slow SCSI drive in wanting a block size of at least 8K to keep > > up with the disk). > > As an aside, AIX uses 4K blocks and doesn't support fragments. AIX uses JFS, which is a journaling file system. Journalling file systems can replay transactions forward, as well as rolling them backward (log structured FS's can only roll them backward). In addition, the very nature of a JFS is significantly different (e.g. to write one for FreeBSD, it would be necessary to cause VOP_ABORTOP to do what it's name says it does, instead of freeing up cn_pnbuf allocations that the caller should be freeing up anyway). Likewise, you can't get rid of the concept of cylinder/cylindergroup without damaging the hashing function, which prevents fragmentation. 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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