My friend was kind enough to give me a 64 gig solid-state disk drive to throw into my development box. I was curious about hard disk speed compared to what I’ve been running: a four-disk RAID5 array of Seagate Barracuda 7200 320GB 7200 RPM SATA (3.0Gb/s) on an Areca ARC-1210 PCI-Express x8 SATA II (3.0Gb/s) Controller Card. Just checked my Newegg order history: the two hard drives are from January 2006, the other two from Sept 2006. I didn’t know they had gotten so old! Haven’t had any failures yet, though.
A few tests (sdb5 = raid5, sda5 = sdd):
sudo hdparm -tT /dev/sdb5
/dev/sdb5:
Timing cached reads: 15534 MB in 1.99 seconds = 7788.19 MB/sec
Timing buffered disk reads: 456 MB in 3.01 seconds = 151.39 MB/sec
sudo hdparm -tT /dev/sda5
/dev/sda5:
Timing cached reads: 14776 MB in 1.99 seconds = 7407.07 MB/sec
Timing buffered disk reads: 558 MB in 3.00 seconds = 185.80 MB/sec
Interesting: the cached throughput on the RAID controller is very good, beating my motherboard controller by a sound 400MB/sec. The reads on the SDD are faster by about 30MB/sec. What about random access seek times? I found some C code to do random seeks. Save the code as seeker.c, and compile with gcc seeker.c -o seeker.
#define _LARGEFILE64_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <time.h>
#include <signal.h>
#include <sys/fcntl.h>
#include <sys/ioctl.h>
#include <linux/fs.h>
#define BLOCKSIZE 4096
#define TIMEOUT 30
int count
;
time_t start
;
void done
()
{
time_t end
;
time(&end
);
if (end
< start
+ TIMEOUT
) {
printf(".");
alarm
(1);
return;
}
if (count
) {
printf(".\nResults: %d seeks/second, %.2f ms random access time\n",
count
/ TIMEOUT
, 1000.0 * TIMEOUT
/ count
);
}
exit(EXIT_SUCCESS
);
}
void handle
(const char *string
, int error
)
{
if (error
) {
perror(string
);
exit(EXIT_FAILURE
);
}
}
int main
(int argc
, char **argv
)
{
char buffer
[BLOCKSIZE
];
int fd
, retval
;
unsigned long numblocks
;
off64_t offset
;
setvbuf(stdout
, NULL
, _IONBF
, 0);
printf("Seeker v2.0, 2007-01-15, "
"http://www.linuxinsight.com/how_fast_is_your_disk.html\n");
if (argc
!= 2) {
printf("Usage: seeker <raw disk device>\n");
exit(EXIT_SUCCESS
);
}
fd
= open
(argv
[1], O_RDONLY
);
handle
("open", fd
< 0);
retval
= ioctl
(fd
, BLKGETSIZE
, &numblocks
);
handle
("ioctl", retval
== -1);
printf("Benchmarking %s [%luMB], wait %d seconds",
argv
[1], numblocks
/ 2048, TIMEOUT
);
time(&start
);
srand(start
);
signal
(SIGALRM
, &done
);
alarm
(1);
for (;;) {
offset
= (off64_t
) numblocks
* random
() / RAND_MAX
;
retval
= lseek64
(fd
, BLOCKSIZE
* offset
, SEEK_SET
);
handle
("lseek64", retval
== (off64_t
) -1);
retval
= read
(fd
, buffer
, BLOCKSIZE
);
handle
("read", retval
< 0);
count
++;
}
/* notreached */
} You need an accurate blocksize; for me, that was 4096.
$ sudo dumpe2fs /dev/sdb5 | grep 'Block size'
dumpe2fs 1.41.14 (22-Dec-2010)
Block size: 4096
So the results?
RAID5:
Seeker v2.0, 2007-01-15, http://www.linuxinsight.com/how_fast_is_your_disk.html
Benchmarking /dev/sdb5 [420909MB], wait 30 seconds..............................
Results: 85 seeks/second, 11.73 ms random access time
SDD:
Seeker v2.0, 2007-01-15, http://www.linuxinsight.com/how_fast_is_your_disk.html
Benchmarking /dev/sda5 [27235MB], wait 30 seconds..............................
Results: 5429 seeks/second, 0.18 ms random access time
The SSD is two orders of magnitude improvement over the RAID5. Not surprising, but still pretty awesome.
Finally, I wanted to migrate my /home directory onto the SSD. This process worked for me:
sudo mkdir /mnt/ocz
sudo mount /dev/sda5 /mnt/ocz
sudo find . -depth -print0 | sudo cpio --null --sparse -pvd /mnt/ocz
sudo mv /home /home_old
sudo mkdir /home
sudo mount /dev/sda5 /home
Don’t forget to add the mount to /etc/fstab so it stays there! Best to use the UUID of the device, so:
11:29 ~ $ sudo blkid
[sudo] password for adam:
/dev/sda5: LABEL="Linux_OCZ" UUID="..." TYPE="ext4"
So /etc/fstab gets another entry, e.g.:
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point> <type> <options> <dump> <pass>
# /home => ocz ssd disk
UUID=... /home ext4 errors=remount-ro 0 1
