Failure writing sector 0x21c8800 to 'hd0'

I suggest you run a full fsck on the file system from live CD /USB.

Hello, thanks for your reply.
Here it is:

ubuntu@ubuntu:~$ sudo parted /dev/sda 'print'
Model: ATA LITEON CV1-8B512 (scsi)
Disk /dev/sda: 512GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number Start End Size File system Name Flags
 1 1049kB 157GB 157GB ntfs msftdata
 2 157GB 158GB 472MB ntfs Basic data partition hidden, diag
 3 158GB 158GB 105MB fat32 EFI system partition boot, esp
 4 158GB 158GB 16.8MB Microsoft reserved partition msftres
 5 158GB 495GB 337GB ext4
 6 495GB 512GB 17.0GB linux-swap(v1)

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ubuntu@ubuntu:~$ sudo fsck -A
fsck from util-linux 2.27.1

ubuntu@ubuntu:~$ sudo fsck -AR -y
fsck from util-linux 2.27.1

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ubuntu@ubuntu:~$ sudo fsck /dev/sda1
fsck from util-linux 2.27.1

ubuntu@ubuntu:~$ sudo fsck /dev/sda2
fsck from util-linux 2.27.1

ubuntu@ubuntu:~$ sudo fsck /dev/sda3
fsck from util-linux 2.27.1
fsck.fat 3.0.28 (2015-05-16)
/dev/sda3: 110 files, 23587/98304 clusters

ubuntu@ubuntu:~$ sudo fsck /dev/sda4
fsck from util-linux 2.27.1
e2fsck 1.42.13 (17-May-2015)
ext2fs_open2: Bad magic number in super-block
fsck.ext2: Superblock invalid, trying backup blocks...
fsck.ext2: Bad magic number in super-block while trying to open /dev/sda4

The superblock could not be read or does not describe a valid ext2/ext3/ext4
filesystem. If the device is valid and it really contains an ext2/ext3/ext4
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>
 or
    e2fsck -b 32768 <device>

ubuntu@ubuntu:~$ sudo fsck /dev/sda5
fsck from util-linux 2.27.1
e2fsck 1.42.13 (17-May-2015)
/dev/sda5: clean, 259254/20586496 files, 13535969/82331648 blocks

ubuntu@ubuntu:~$ sudo fsck /dev/sda6
fsck from util-linux 2.27.1

Please bear in mind that during the last two months I wiped completely my SSD already 5-6 times. After making an Ubuntu 16.04 clean installation, this error appears right after the first turning off/on.

If it can help, here is my DMESG output:

http://lists.gnu.org/archive/html/bug-grub/2016-06/txtqz_EG2yzRl.txt

I'm certainly not an expert, so here's some interesting Google results:

'failure writing to sector'
This bug was fixed in the package grub2 - 1.99-21ubuntu3.15
https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1253443

aljosa wrote: "I installed Xenial for the first time at the beginning of February. Initially I didn't have this error."
user wrote: "I finally got down to do some debugging. failure writing sector corresponds to GRUB_EFI_NO_MEDIA."
GRUB patch introduced in February: "GRUB_EFI_NO_MEDIA" https://lists.gnu.org/archive/html/grub-devel/2016-02/msg00018.html

My qustion still remains unanswered: 'failure writing to sector' issue is caused by GRUB or by something else?

The superblock is corrupt, such showed :

ext2fs_open2: Bad magic number in super-block
fsck.ext2: Superblock invalid, trying backup blocks...
fsck.ext2: Bad magic number in super-block while trying to open /dev/sda4

The superblock could not be read or does not describe a valid ext2/ext3/ext4
filesystem. If the device is valid and it really contains an ext2/ext3/ext4
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>
 or
    e2fsck -b 32768 <device>
********************************************************************
As the program sugests try this :
e2fsck -b 8193 <device>
or
e2fsk -b 32768 <device>

if not results, then I sugest for you makes backup of entire disk
and when install linux again, delete ALL table partition and make
a new formatation SLOW with badblocks Enabled. ( USE LINUX FOR THIS JOB ! )

Ronaldo wrote: "The superblock is corrupt, such showed: The superblock could not be read or does not describe a valid ext2/ext3/ext4 filesystem. If the device is valid and it really contains an ext2/ext3/ext4 filesystem (and not swap or ufs or something else), then the superblock is corrupt".
The fact is that dev/sda4 does not contain ext2/ext3/ext4 filesystem, but something else, which is Microsoft reserved partition msftres.

Maybe I'm wrong, but sane basic logic suggests me that corrupted superblock is totally unimportant because it does not occur without installing Windows, which was my situation already 5-6 times during the last two months when I wiped completely my SSD (including deleting of ALL table partition and making of new formatation) and installed only Ubuntu. Furthermore, the fact is that I'm not the only one with Lenovo Y700 who suffer 'failure writing sector' bug.

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