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Linux and 4096-Byte Sector Hard Drives
14.02.10
Linux and 4096-Byte Sector Hard Drives
New hard drives uses 4k-byte sector but devices cheat on linux and say that they're using 512-byte sector as usual. If partitions are not aligned to 8 blocks, there's a huge throughput degradation. Use the 'expert' menu [x] on fdisk to move beginning of data in a partition [b] and align it to 8 blocks.
Test program:
#define _LARGEFILE64_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#define N 4096
char buffer[N];
int main(int argc, char *argv[])
{
int fd, i, j;
char *file = "test.dat";
int size = 2048;
printf ("usage: %s <file> <#blocs>\n", argv[0]);
if (argc > 1) file = argv[1];
if (argc > 2) size = atoi (argv[2]);
fd = open(file, O_WRONLY | O_CREAT | O_TRUNC | O_SYNC);
printf ("open %s (fd=%d)\n", file, fd);
if (fd <= 0) return 1;
printf ("write %dx%d=%d data\n", size, N, size * N);
for (i = 0; i < size; i++) {
int rand = random ();
for (j = 0; j < N; j++, rand = (rand << 1) ^ (rand >> sizeof (int)))
buffer[j] ^= rand;
write(fd, buffer, N);
}
close(fd);
return 0;
}
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