root@srv1:~# grep data /proc/mounts
/dev/md124 /mnt/data ext4
rw,noatime,nodiratime,user_xattr,acl,barrier=1,data=ordered 0 0
root@srv1:~# grep md124 /proc/mdstat
md124 : active raid1 sdb4[0] sda4[2]
root@srv1:~# smartctl -i /dev/sda|grep odel
Device Model: ST1000DM003-9YN162
root@srv1:~# smartctl -i /dev/sdb|grep odel
Device Model: ST1000DM003-9YN162
root@srv1:~# truncate -s 1G /mnt/data/tmp/deleteme
root@srv1:~# losetup -f /mnt/data/tmp/deleteme
root@srv1:~# parted /dev/loop0 'mktable msdos'; parted /dev/loop0 'mkpart p
0% 100%'
root@srv1:~# kpartx -a /dev/loop0
root@srv1:~# dd if=/dev/zero |pv -rab|dd of=/dev/mapper/loop0p1
^C46MB [43.6MB/s] [44.6MB/s]
946836+0 records in
946835+0 records out
484779520 bytes (485 MB) copied, 10.6719 s, 45.4 MB/s
root@srv1:~# dd if=/dev/zero bs=64M |pv -rab|dd bs=64M
of=/dev/mapper/loop0p1 conv=fsync oflag=direct,sync,nonblock
dd: warning: partial read (131072 bytes); suggest iflag=fullblock
^C59MB [1.86MB/s] [1.25MB/s]B/s]
0+478 records in
0+478 records out
62652416 bytes (63 MB) copied, 47.4236 s, 1.3 MB/s
[atop fara sync]
LVM | loop0p1 | busy 33% | read 10227 | write 18668 |
MBw/s 72.92 | avio 0.01 ms |
[atop cu sync]
LVM | loop0p1 | busy 97% | read 0 | write 660 |
MBw/s 2.50 | avio 1.48 ms |
[nmon fara sync]
|DiskName Busy Read Write Xfers Size Peak% Peak-RW
InFlight |
|dm-0 29% 44318.0 64316.8KB/s 27158.7 4.0KB 101% 120569.4KB/s
0 |
[nmon cu sync]
|DiskName Busy Read Write Xfers Size Peak% Peak-RW
InFlight |
|dm-0 99% 0.0 1534.5KB/s 395.6 3.9KB 101% 2174.2KB/s 1
|
daca repet testele cu un loop peste fisier normal (NU sparse!), nu se mai
observa citiri din loop0p1 atunci cand scriu in el cu dd.
de asemenea daca fac testele direct pe fisier (fie sparse, fie normal), nu
se observa decat scrieri.
imi poate explica cineva cu capul ceva mai mare decat al meu care este
cauza pentru care atunci cand sub loop e un fisier sparse, scrierile cu dd
pe acel blockdevice sunt insotite de citiri?
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