Date: Tue, 3 Apr 2001 02:41:56 -0500 From: Mike Meyer <mwm@mired.org> To: Andrew Hesford <ajh3@chmod.ath.cx> Cc: questions@freebsd.org Subject: Re: disklabel and block size Message-ID: <15049.32452.121199.981277@guru.mired.org> In-Reply-To: <73940366@toto.iv>
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Andrew Hesford <ajh3@chmod.ath.cx> types: > I have two related questions: > 1. In the disklabel output, what is the significance of the bps/cpg > group? The man page for disklabel says that for disks larger than 1G, it > defaults to 64, but mine is 16, and an example in the man page had it > set at 75. What does this field mean, and how will different values > affect the disk? This one is in the man page for disklabel, and is the "cylinders per group" of the filesystem. FFS divides a partition up into "cylinder groups". Each group has it's own segment of the inode list. A best attempt is made to allocate all file data in the same cylinder group, and to keep the entries in a directory in that cylinder group. This means head motion when reading a file is potentially restricted to that cylinder group, and not scattered over the entire partition. Basically, it's one of the reasons that you don't need to defrag your drive like you do on windows. All the blocks are already close together. <mike -- Mike Meyer <mwm@mired.org> http://www.mired.org/home/mwm/ Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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