VTOC

SPARCアーキテクチャでは、HDDの先頭にディスクラベルがあり、ディスクラベルに含まれるVTOCによりスライスが定義されている。

ディスクラベル

dklabel.hで以下のように定義されている

/*
 * Miscellaneous defines
 */
#define DKL_MAGIC 0xDABE /* magic number */
#define FKL_MAGIC 0xff   /* magic number for DOS floppies */
#define DKMAP     8      /* # of logical partitions */

/*
 * Format of a Sun SMD disk label.
 * Resides in cylinder 0, head 0, sector 0.
 *
 * sizeof (struct dk_label) should be 512 (sector size)
 */
struct dk_label {
    char dkl_asciilabel[128];   /* for compatibility */
    char dkl_pad[512-(128+NDKMAP*8+14*2)];
    unsigned short dkl_rpm;     /* rotations per minute */
    unsigned short dkl_pcyl;    /* # physical cylinders */
    unsigned short dkl_apc;     /* alternates per cylinder */
    unsigned short dkl_obs1;    /* obsolete */
    unsigned short dkl_obs2;    /* obsolete */
    unsigned short dkl_intrlv;  /* interleave factor */
    unsigned short dkl_ncyl;    /* # of data cylinders */
    unsigned short dkl_acyl;    /* # of alternate cylinders */
    unsigned short dkl_nhead;   /* # of heads in this partition */
    unsigned short dkl_nsect;   /* # of 512 byte sectors per track */
    unsigned short dkl_obs3;    /* obsolete */
    unsigned short dkl_obs4;    /* obsolete */
    /* */
    struct dk_map {             /* logical partitions */
        daddr_t dkl_cylno;      /* starting cylinder */
        daddr_t dkl_nblk;       /* number of blocks */
    } dkl_map[NDKMAP];
    unsigned short dkl_magic;   /* identifies this label format */
    unsigned short dkl_cksum;   /* xor checksum of sector */
};

ディスクラベルを読み出してみる

# dd if=/dev/rdsk/c0t0d0s2 of=disk_label count=1

読み出した実際のデータを定義に当てはめてみる

dkl_asciilabel = "ST320011A cyl 38790 alt 2 hd 16 sec 63"
dkl_pad = .......
dkl_rpm = 0x1518 = 5400
dkl_pcyl =  0x9788 = 38792
dkl_apc = 0x0000
dkl_obs1 = 0x0000
dkl_obs2 = 0x0000
dkl_intrlv = 0x0001
dkl_ncyl = 0x9786 = 38790
dkl_acyl = 0x0002
dkl_nhead = 0x0010 = 16
dkl_nsect = 0x003F = 63
dkl_obs3 = 0x0000
dkl_obs4 = 0x0000
dkl_map[0].dkl_cylno = 0x00002DB1 = 11697
dkl_map[0].dkl_nblk = 0x01A0B6B0 = 27309744
dkl_map[1].dkl_cylno = 0x00000000
dkl_map[1].dkl_nblk = 0x000FFF00 = 1048320
dkl_map[2].dkl_cylno = 0x00000000
dkl_map[2].dkl_nblk = 0x02549FA0 = 39100320
dkl_map[3].dkl_cylno = 0x00000000
dkl_map[3].dkl_nblk = 0x00000000
dkl_map[4].dkl_cylno = 0x00000000
dkl_map[4].dkl_nblk = 0x00000000
dkl_map[5].dkl_cylno = 0x00000000
dkl_map[5].dkl_nblk = 0x00000000
dkl_map[6].dkl_cylno = 0x00000000
dkl_map[6].dkl_nblk = 0x00000000
dkl_map[7].dkl_cylno = 0x00000410 = 1040
dkl_map[7].dkl_nblk = 0x00A3E9F0 = 10742256
dkl_magic = 0xDABE
dkl_cksum = 0x002A

prtvtocコマンドから得られる値

# prtvtoc /dev/rdsk/c0t0d0s2
* /dev/rdsk/c0t0d0s2 partition map
*
* Dimensions:
*     512 bytes/sector
*      63 sectors/track
*      16 tracks/cylinder
*    1008 sectors/cylinder
*   38792 cylinders
*   38790 accessible cylinders
*
* Flags:
*   1: unmountable
*  10: read-only
*
*                          First     Sector    Last
* Partition  Tag  Flags    Sector     Count    Sector  Mount Directory
       0      2    00   11790576  27309744  39100319   /
       1      3    01          0   1048320   1048319
       2      5    00          0  39100320  39100319
       7      8    00    1048320  10742256  11790575   /export/home

実はVTOCはもうオワコン気味で、2TBを超えるHDDを扱う場合は下記を参照。

ディスクラベルについて - Oracle Solaris の管理: デバイスとファイルシステム