Strange write speed between /file and /tmp/file (may be related to 4k advanced format)

[Patrick Dung]

Hi,

I have a FreeBSD 9.2 64 bit installed in a VM.
The host is Windows 7 with vmware workstation, the host is using an advanced format (4k) harddisk.


I have noticed there is strange write speed between /file and /tmp/file.
/dev/da0p3 is UFS2 created by default installer.

I am thinking if the problem is caused by disk alignment.
da0p3 starting sector is 786594, which seems not aligned by 4k (786594 *512/4096=98324.25)
The dd result is repeatable.


[root at testing2 /]# df -P
Filesystem 512-blocks      Used     Avail Capacity  Mounted on
/dev/da0p3    6518712   4621000   1376216    77%    /
devfs               2         2         0   100%    /dev
fdescfs             2         2         0   100%    /dev/fd
procfs              8         8         0   100%    /proc
host:hgfs   591368064 405571456 185796608    69%    /mnt-hgfs
[root at testing2 /]# gpart show da0
=>     34  7548861  da0  GPT  (3.6G)
       34      128    1  freebsd-boot  (64k)
      162   786432    2  freebsd-swap  (384M)
   786594  6760448    3  freebsd-ufs  (3.2G)
  7547042     1853       - free -  (926k)

[root at testing2 /]# dd if=/dev/zero of=/tmp/file bs=50M count=4
4+0 records in
4+0 records out
209715200 bytes transferred in 10.303288 secs (20354202 bytes/sec)
[root at testing2 /]# rm /tmp/file
[root at testing2 /]# dd if=/dev/zero of=/tmp/file bs=50M count=4
4+0 records in
4+0 records out
209715200 bytes transferred in 9.789672 secs (21422087 bytes/sec)
[root at testing2 /]# rm /tmp/file
[root at testing2 /]# ~^C
[root at testing2 /]# dd if=/dev/zero of=/file bs=50M count=4
4+0 records in
4+0 records out
209715200 bytes transferred in 6.826694 secs (30719877 bytes/sec)
[root at testing2 /]# rm /file
[root at testing2 /]# dd if=/dev/zero of=/file bs=50M count=4
4+0 records in
4+0 records out
209715200 bytes transferred in 6.955417 secs (30151348 bytes/sec)
[root at testing2 /]# rm /file

Thanks and regards,
Patrick Dung