On Sun, Mar 4, 2012 at 6:06 PM, Pandu Poluan <pa...@poluan.info> wrote: > > On Mar 5, 2012 4:59 AM, "Grant" <emailgr...@gmail.com> wrote: >> >> >> All my drives says this from fdisk: >> >> Units = sectors of 1 * 512 = 512 bytes >> Sector size (logical/physical): 512 bytes / 512 bytes >> I/O size (minimum/optimal): 512 bytes / 512 bytes >> >> So it doesn't matter where the first partition starts? >> > > Older BIOSes don't understand that hard disks now can have 4KiB sectors, so > some of the "advanced format" hard disks report a sector size of 512B. But > behind the scenes, the hard disk maps the logical sector to a subsector of > the physical sector. > > The only sure fire way to find out if your hard disk uses 4KiB sectors is to > open your computer and eyeball the hard disk. All 4KiB hard disks that I > know of have statements on their surface that tell me so. > > Rgds,
I think I must be kind of late to this conversation, but as background consider hdparm -i coupled with Google for the actual spec: c2stable ~ # hdparm -i /dev/sdg /dev/sdg: Model=WDC WD10EARS-00Z5B1, FwRev=80.00A80, SerialNo=WD-WCAVU0415076 Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq } RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=50 BuffType=unknown, BuffSize=unknown, MaxMultSect=16, MultSect=off CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=1953525168 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120} PIO modes: pio0 pio3 pio4 DMA modes: mdma0 mdma1 mdma2 UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6 AdvancedPM=no WriteCache=enabled Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5,6,7 * signifies the current active mode c2stable ~ # With the model number it takes only a minute to determine that this WD drive is a 4K sector drive. (Which is marked on the drive, as you state, but I'd have to remove it to find that out.) Now, in terms of performance, the only requirement (as I understand it) is that all drive partition be aligned to sector addresses divisible by 8. (512 * 8 = 4K) The reason 63 gives low performance is because it's not naturally aligned by 8. With older versions of fdisk if I started the first partition at 64 then the performance was fine and only one sector was wasted. M$, for whatever reason, decided to start at 2048, which is divisible by 8, reserving the area at the front of the drive for (I think) their boot loader and other M$-y things. My understanding of why fdisk now enforces this is simply to be more careful about not overwriting the M$ boot loaderif it's there. (But I could be very wrong about that!) Remember, it's possible to make a dual boot system using M$'s loader instead of grub, and important that fdisk doesn't mangle it when someone is using that tool. Just my views, Mark