On Tue, Dec 17, 2013 at 4:12 AM, Stephen Powell <zlinux...@wowway.com> wrote: > On Mon, 16 Dec 2013 08:13:16 -0600, Stan Hoeppner wrote: >> >> Cool. Make sure you partition the SSD so that your first, and all, >> partitions start on a 4KB boundary. Many guides are available for your >> favorite partitioning tool. Linux does all IO in 4KB pages including >> filesystem and swap. If you don't align to 4KB you may get excessive >> erase cycles on the SSD, lowering performance, and cell life. Most >> folks seem to start the first SSD partition at sector 2048, which falls >> immediately after the first 1MB of the device. 1,048,576/4,096=256. So >> your first partition will start at 4KB "page 257", if you will. If you >> create multiple partitions, make sure the size of each is evenly >> divisible by 4096 bytes, or they won't be aligned. > > That's good to know. But I really don't have much control over this > when I partition using the Debian installer. When installing from > scratch on a system where I don't intend to keep anything from its > previous life, I delete all existing partitions using the Debian installer, > then create new partitions using the Debian installer. When I create > a new partition with the Debian installer, I generally specify the size > (typically in megabytes), the partition type (primary or logical), and, > if the size is less than the amount of free space, whether I want it at > the beginning of the free space or the end of the free space. Rounding > of sizes, boundary alignment, etc. is all controlled by the Debian installer > or the partitioning tools it uses (parted, generally). And I have no > control over that. > > As an example, my existing disk partitions, created by the Debian installer, > look like this: > > # parted /dev/i2o/hda unit s print free > Model: I2O Controller (i2o) > Disk /dev/i2o/hda: 286748672s > Sector size (logical/physical): 512B/512B > Partition table: msdos > > Number Start End Size Type File system Flags > 63s 2047s 1985s Free Space > 1 2048s 194559s 192512s primary ext3 boot > 194560s 196605s 2046s Free Space > 2 196606s 162306302s 162109697s extended > 5 196608s 17772543s 17575936s logical linux-swap(v1) > 6 17774592s 56834047s 39059456s logical ext3 > 7 56836096s 64647167s 7811072s logical ext3 > 8 64647231s 162306302s 97659072s logical ext3 > 162306303s 286748671s 124442369s Free Space > > # > > As you can see, something, somewhere, has done a number on me. The only > boundary requirement is that the starting sector be a multiple of 8 to make > 4096-byte boundaries. So why start the first partition at sector number > 2048? The only intentional free space is the free space at the end of the > disk. The other free space entries were added by the partitioning program. > And for what purpose? This is not a GPT disk, so no BIOS boot partition > needs to be created for GRUB. (I'm not even using GRUB, I'm using LILO. > But the Debian installer would not have known what boot loader I planned > to use during the disk partitioning phase. It would, however, have known > that this is an MBR disk, not a GPT disk.) Furthermore, this is not a > UEFI-based system, so no EFI System partition (ESP) needs to be created > either. So why did the Debian installer leave these two free spaces before > and after my first partition? (Apparently, sectors 0-62 are considered part > of "meta data" and are therefore not included in the leading free space.) > > Also, as you can see, the start of the next partition is not just one sector > number higher than the end of the previous partition. In the case of adjacent > logical partitions inside the extended partition, I realize that it must > leave room for an Extended Boot Record before each logical partition, but it > leaves way more room than that would require. Can you (or anyone) explain > why this wasted space has been built in?
Current practice is that all partitions should start at a multiple of 1 MiB in order for these partitions to be aligned with different types of hardware. Your data partitions #1,5,6,7 start on a multiple of 2048s, hence the gaps between them and the gap before #1. Somehow #7 and #8 only have a gap of 63s between them. Did you create #8 via d-i or post-install? Regarding the 0-62 sectors: the "specialness" of these sectors is historical because sector 0 contained the MBR and the first partition started at the second track - and there were 63 sectors per track. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/CAOdo=szhoh8hb_5-d_zwm7s6_k5jt4bw_nhvsxetdveaoxs...@mail.gmail.com