Here are the answers to your questions
1. fsck does not report any error and the file contained inside the FS is definitely greater than the allocatable LV size # fsck.ext4 -f -C0 /dev/virtp/vol01
e2fsck 1.43-WIP (15-Mar-2016)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/virtp/vol01: 12/65536 files (8.3% non-contiguous), 30492/262144 blocks
# du -hs fil
69M fil
(please note here that the LV virtual size is 1G but the parent pool size is just 40M I expect the file not to exceed 40M at any cost.)
3. lvs # lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
virtpool virtp twi-aotzD- 40.00m 100.00 1.37
vol01 virtp Vwi-aotz-- 1.00g virtpool
You can do this on any virtual machine. I use qemu with virtio back-end.
On Tue, May 3, 2016 at 11:54 AM, Zdenek Kabelac <zkabelac@redhat.com> wrote:
On 3.5.2016 08:59, Bhasker C V wrote:
Does this mean the ext4 is showing wrong information. The file is reported
being 90+MB but in actuality the size is less in the FS ?
This is quite ok because it is just that file system being affected. I was
however concerned that the file in this FS might have overwritten other LV
data since the file is showing bigger than the volume size.
I've no idea what 'ext4' is showing you, but if you have i.e. 100M filesystem size, you could still have there e.g. 1TB file. Experience the magic:
'truncate -s 1T myfirst1TBfile'
As you can see 'ext4' is doing it's own over-provisioning with 'hole' files.
The only important bits are:
- is the filesystem consistent ?
- is 'fsck' not reporting any error ?
What's the 'real' size you get with 'du myfirst1TBfile' or your wrong file ?
Somehow I don't believe you can get i.e. 90+MB 'du' size with 10MB filesystem size and 'fsck' would not report any problem.
I will try this using BTRFS.
For what exactly ??
Regard
Zdenek
On Fri, Apr 29, 2016 at 10:13 AM, Zdenek Kabelac <zkabelac@redhat.comlinux-lvm@redhat.com <mailto:linux-lvm@redhat.com><mailto:zkabelac@redhat.com>> wrote:
On 28.4.2016 16:36, Bhasker C V wrote:
Zdenek,
Thanks. Here I am just filling it up with random data and so I am not
concerned about data integrity
You are right, I did get page lost during write errors in the kernel
The question however is even after reboot and doing several fsck of
the ext4fs
the file size "occupied" is more than the pool size. How is this ?
I agree that data may be corrupted, but there *is* some data and this
must be
saved somewhere. Why is this "somewhere" exceeding the pool size ?
Hi
Few key principles -
1. You should always mount extX fs with errors=remount-ro (tune2fs,mount)
2. There are few data="" modes ensuring various degree of data integrity,
An case you really care about data integrity here - switch to 'journal'
mode at price of lower speed. Default ordered mode might show this.
(i.e. it's the very same behavior as you would have seen with failing hdd)
3. Do not continue using thin-pool when it's full :)
4. We do miss more configurable policies with thin-pools.
i.e. do plan to instantiate 'error' target for writes in the case
pool gets full - so ALL writes will be errored - as of now - writes
to provisioned blocks may cause further filesystem confusion - that's
why 'remount-ro' is rather mandatory - xfs is recently being enhanced
to provide similar logic.
Regards
Zdenek
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