On 12/11/2014 02:25 AM, Goffredo Baroncelli wrote:
On 12/10/2014 11:53 AM, Robert White wrote:
On 12/09/2014 05:08 PM, Dongsheng Yang wrote:
On 12/10/2014 02:47 AM, Goffredo Baroncelli wrote:
Hi Dongsheng On 12/09/2014 12:20 PM, Dongsheng Yang wrote:
When function btrfs_statfs() calculate the tatol size of fs, it
is calculating the total size of disks and then dividing it by
a factor. But in some usecase, the result is not good to user.
Example: # mkfs.btrfs -f /dev/vdf1 /dev/vdf2 -d raid1 # mount
/dev/vdf1 /mnt # dd if=/dev/zero of=/mnt/zero bs=1M count=1000
# df -h /mnt Filesystem Size Used Avail Use% Mounted on
/dev/vdf1 3.0G 1018M 1.3G 45% /mnt
# btrfs fi show /dev/vdf1 Label: none uuid:
f85d93dc-81f4-445d-91e5-6a5cd9563294 Total devices 2 FS bytes
used 1001.53MiB devid 1 size 2.00GiB used 1.85GiB path
/dev/vdf1 devid 2 size 4.00GiB used 1.83GiB path /dev/vdf2
a. df -h should report Size as 2GiB rather than as 3GiB.
Because this is 2 device raid1, the limiting factor is devid 1
@2GiB.
I agree
NOPE.
The model you propose is too simple.
While the data portion of the file system is set to RAID1 the
metadata portion of the filesystem is still set to the default of
DUP. As such it is impossible to guess how much space is "free" since
it is unknown how the space will be used before hand.
Hi Robert,
sorry but you are talking about a different problem.
Yang is trying to solve a problem where it is impossible to fill
all the disk space because some portion is not raid1 protected. So
it is incorrect to report all space/2 as free space.
Instead you are stating that *if* the metadata are stored as DUP (and
is not this case, because the metadata are raid1, see below), it is possible
to fill all the disk space.
This is a complex problem. The fact that BTRFS allows different
raid levels causes to be very difficult to evaluate the free space (
as space available directly to the user). There is no a simple answer.
I am still convinced that the best free space *estimation* is considering
the ratio disk-space-consumed/file-allocated constant, and evaluate
the free space as the
disk-space-unused*file-allocate/disk-space-consumed.
Of course there are pathological cases that make this
prediction fails completely. But I consider the best estimation
possible for the average users.
But again this is a different problem that the one raised by
Yang.
Thanx Goffredo, I have cooked a v2 for this problem. I will send it out
soon.
[...]
IF you wanted everything to be RAID-1 you should have instead done
# mkfs.btrfs -f /dev/vdf1 /dev/vdf2 -d raid1 -m raid1
The mistake is yours, rest of you analysis is, therefore, completely
inapplicable. Please read all the documentation before making that
sort of filesystem. Your data will thank you later.
DSCLAIMER: I have _not_ looked at the numbers you would get if you
used the corrected command.
Sorry, but you are wrong. Doing mkfs.btrfs -d raid1 /dev/loop[01] leads
to have both data and metadata in raid1. IIRC if you have more than
one disks, the metadata switched to raid1 automatically.
$ sudo mkfs.btrfs -d raid1 /dev/loop[01]
Btrfs v3.17
See http://btrfs.wiki.kernel.org for more information.
Performing full device TRIM (10.00GiB) ...
Turning ON incompat feature 'extref': increased hardlink limit per file to 65536
Performing full device TRIM (30.00GiB) ...
adding device /dev/loop1 id 2
fs created label (null) on /dev/loop0
nodesize 16384 leafsize 16384 sectorsize 4096 size 40.00GiB
ghigo@venice:/tmp$ sudo mount /dev/loop0 t/
ghigo@venice:/tmp$ sudo dd if=/dev/zero of=t/fill bs=4M count=10
10+0 records in
10+0 records out
41943040 bytes (42 MB) copied, 0.018853 s, 2.2 GB/s
ghigo@venice:/tmp$ sync
ghigo@venice:/tmp$ sudo btrfs fi df t/
Data, RAID1: total=1.00GiB, used=40.50MiB
Data, single: total=8.00MiB, used=0.00B
System, RAID1: total=8.00MiB, used=16.00KiB
System, single: total=4.00MiB, used=0.00B
Metadata, RAID1: total=1.00GiB, used=160.00KiB
Metadata, single: total=8.00MiB, used=0.00B
GlobalReserve, single: total=16.00MiB, used=0.00B
[...]
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