Files containing only zeroes gets modified after restart

[PeterC]

Hi,

I would like to report that files containing only zeroes, gets modified after turning the virtual machine off and on.

Before the restart:

piotrek@sue:~> dd if=/dev/zero of=zeroes_1GB bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 0,678558 s, 1,6 GB/s
piotrek@sue:~> cmp /dev/zero zeroes_1GB
cmp: EOF on zeroes_1GB

After the restart:

piotrek@sue:~> cmp /dev/zero zeroes_1GB
/dev/zero zeroes_1GB differ: byte 647411201, line 1

The place of the first difference seems to be pretty much random. This can be illustrated by another example.

Before the restart:

piotrek@sue:~> for i in {1..10}; do dd if=/dev/zero of=zeroes_1GB_$i bs=1M count=1024; done
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 0,62127 s, 1,7 GB/s
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 1,80431 s, 595 MB/s
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 3,4662 s, 310 MB/s
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 3,16451 s, 339 MB/s
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 3,0117 s, 357 MB/s
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 3,51445 s, 306 MB/s
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 2,57957 s, 416 MB/s
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 6,12661 s, 175 MB/s
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 7,04536 s, 152 MB/s
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 5,41265 s, 198 MB/s

piotrek@sue:~> for i in {1..10}; do cmp /dev/zero zeroes_1GB_$i; done
cmp: EOF on zeroes_1GB_1
cmp: EOF on zeroes_1GB_2
cmp: EOF on zeroes_1GB_3
cmp: EOF on zeroes_1GB_4
cmp: EOF on zeroes_1GB_5
cmp: EOF on zeroes_1GB_6
cmp: EOF on zeroes_1GB_7
cmp: EOF on zeroes_1GB_8
cmp: EOF on zeroes_1GB_9
cmp: EOF on zeroes_1GB_10

After the restart:

piotrek@sue:~> for i in {1..10}; do cmp /dev/zero zeroes_1GB_$i; done
/dev/zero zeroes_1GB_1 differ: byte 794570753, line 1
/dev/zero zeroes_1GB_2 differ: byte 242036737, line 1
/dev/zero zeroes_1GB_3 differ: byte 184365057, line 1
/dev/zero zeroes_1GB_4 differ: byte 10874881, line 1
/dev/zero zeroes_1GB_5 differ: byte 460075009, line 1
/dev/zero zeroes_1GB_6 differ: byte 48693249, line 1
/dev/zero zeroes_1GB_7 differ: byte 101187585, line 1
cmp: EOF on zeroes_1GB_8
cmp: EOF on zeroes_1GB_9
cmp: EOF on zeroes_1GB_10

When I cat one of the files, I recognize the content that is normally on my disk (for example xml requests that I store).

VirtualBox version: 5.1.12 r112440 (Qt5.6.2)

Host: Windows 7

Guest: OpenSuse 42.2

Linux kernel version: 4.4.104-18.44-default

Laptop: Dell Precision 3510

Screenshots of applicable virtual machine settings attached.

Best regards,

Piotr

[PeterC]

Screenshot of the settings of SATA controller

[PeterC]

Screenshot of the settings of the virtual disc