Rob Bray wrote:
I am trying to grow a raid5 volume in-place. I would like to expand the
partition boundaries, then grow raid5 into the newly-expanded partitions.
I was wondering if there is a way to move the superblock from the end of
the old partition to the end of the new partition. I've tried dd
if=/dev/sdX1 of=/dev/sdX1 bs=512 count=256
skip=(sizeOfOldPartitionInBlocks - 256) seek=(sizeOfNewPartitionInBlocks -
256) unsuccessfully. Also, copying the last 128KB (256 blocks) of the old
partition before the table modification to a file, and placing that data
at the tail of the new partition also yields no beans. I can drop one
drive at a time from the group, change the partition table, then hot-add
it, but a resync times 7 drives is a lot of juggling. Any ideas?
The superblock location is somewhat tricky to calculate correctly.
I've used a tiny program (attached) for exactly this purpose.
/mjt
/* mdsuper: read or write a linux software raid superbloc (version 0.90)
* from or to a given device.
*
* GPL.
* Written by Michael Tokarev ([EMAIL PROTECTED])
*/
#define _GNU_SOURCE
#include sys/types.h
#include stdio.h
#include unistd.h
#include errno.h
#include stdlib.h
#include fcntl.h
#include string.h
#include sys/ioctl.h
#include linux/ioctl.h
#include linux/types.h
#include linux/raid/md_p.h
#include linux/fs.h
int main(int argc, char **argv) {
unsigned long long dsize;
unsigned long long offset;
int mdfd;
int n;
mdp_super_t super;
const char *dev;
if (argc != 3) {
fprintf(stderr, mdsuper: usage: mdsuper {read|write} mddev\n);
return 1;
}
if (strcmp(argv[1], read) == 0)
n = O_RDONLY;
else if (strcmp(argv[1], write) == 0)
n = O_WRONLY;
else {
fprintf(stderr, mdsuper: read or write arg required, not \%s\\n,
argv[1]);
return 1;
}
dev = argv[2];
mdfd = open(dev, n, 0);
if (mdfd 0) {
perror(dev);
return 1;
}
if (ioctl(mdfd, BLKGETSIZE64, dsize) 0) {
perror(dev);
return 1;
}
if (dsize MD_RESERVED_SECTORS*2) {
fprintf(stderr, mdsuper: %s is too small\n, dev);
return 1;
}
offset = MD_NEW_SIZE_SECTORS(dsize9);
fprintf(stderr, size=%Lu (%Lu sect), offset=%Lu (%Lu sect)\n,
dsize, dsize9, offset * 512, offset);
offset *= 512;
if (n == O_RDONLY) {
if (pread64(mdfd, super, sizeof(super), offset) != sizeof(super)) {
perror(dev);
return 1;
}
if (super.md_magic != MD_SB_MAGIC) {
fprintf(stderr, %s: bad magic (0x%08x, should be 0x%08x)\n,
dev, super.md_magic, MD_SB_MAGIC);
return 1;
}
if (write(1, super, sizeof(super)) != sizeof(super)) {
perror(write);
return 1;
}
}
else {
if (read(0, super, sizeof(super)) != sizeof(super)) {
perror(read);
return 1;
}
if (pwrite64(mdfd, super, sizeof(super), offset) != sizeof(super)) {
perror(dev);
return 1;
}
}
return 0;
}
