On Wed, 2006-04-19 at 20:25 +0200, Ingemar Nilsson wrote: > Lyvim Xaphir <knightmerc@xxxxxxxxx> writes: > > > the first place. First spot is the first spot. First drive, and also > > the first sectors of the hard drive, the prime real estate of the drive > > where the accesses are faster. > > Could you elaborate on why disk accesses are faster in the first sectors of > the hard drive? > > Regards > Ingemar > A drive's sectors actually start out on the rim of the drive. In that area, you have more sectors per track (outer rim) than as you go closer towards the spindle. At the spindle you have the lowest sectors per track. Both the data rate and the sectors per track are greatest at the rim of the hard drive; which is where the boot sector is too btw. The heads can stay on one track and transfer more contiguous data per cylinder on cylinders at the rim than they can close to the spindle. There is a progression of data rate from greatest (rim) to lowest (spindle). LBA 0 is at the outermost rim and maximum LBA is at the spindle of the drive. Therefore for maximum performance utilization of a hard drive, the layout should go like this (as an example): [root@localhost bin]# fdisk -l /dev/sdb Disk /dev/sdb: 82.3 GB, 82348277760 bytes 255 heads, 63 sectors/track, 10011 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 * 1 10011 80413326 85 Linux extended /dev/sdb5 (boot) 1 6 48132 fd Linux raid autodetect /dev/sdb6 (root) 7 50 353398+ fd Linux raid autodetect /dev/sdb7 (swap) 51 84 273073+ fd Linux raid autodetect /dev/sdb8 (tmp) 85 158 594373+ fd Linux raid autodetect /dev/sdb9 (usr) 159 456 2393653+ fd Linux raid autodetect /dev/sdb10 (var) 457 10011 76750506 fd Linux raid autodetect This is one drive of a raid-0 array. /boot is raid-1 cause lilo is unable to handle /boot partitions at raid-0. It's better to have boot mirrored rather than striped anyway. I place /boot at the absolute beginning because putting the boot partition there above the 1024 cylinder boundary sidesteps problems with some bioses that have difficulty dealing with boot stuff over that boundary. Root is the first partition mounted and has some binaries used during the boot process, plus it takes up a very negligible amount of room (600 megs) when compared with this drive example, which is 80 gigabytes. Swap is placed immediately after /root, and thus takes advantage of the data rate in the forward sectors of the drive. /tmp filesystem has the highest rate of filesystem change, so it's prioritized right after swap. /usr of course has the lion's share of binaries utilized in desktop mode so it has the next priority. /Var then occupies the rest of the drive (and the major part of it). In this configuration, /home is symlinked to /var/home. There are many reasons for doing this but the main one is that logfiles don't become a problem and neither does the space occupied by users in /var/home. I did an informal study of filesystem activity back in the late 90's and /var and /home were the most similar in that regard. Rate of filesystem activity corresponds closely to the risk of filesystem corruption. Thus we generally separate (filesystems) according to rate of file change; therefore boxing the greater risk factors in their own private domains so that they are not shared. I should also note that space utilization becomes too inefficient on a desktop box when you separate /home and /var. This configuration was arrived at after a very long time of careful deliberation over hard drive performance, filesystem corruption risks, and concerns over most efficient utilization of hard drive space. I hope this answered your question. Best Regards LX -- °°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°° A wise person makes his own decisions, a weak one obeys public opinion. -- Chinese proverb Registered Linux User #268899 http://counter.li.org/ °°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°
