This is with reserved_ratio set to 20 in /etc/mke2fs.conf for easy
identification of what's happening:
Default 10G container:
# vzctl create 9999 --ostemplate centos-7-x86_64 --diskspace 100G
# tune2fs -l /dev/ploop43211p1 |grep -i 'block count'
Block count: 26213888
Reserved block count: 1074721
This is 5%
#vzctl set 9999 --diskspace 200G --save
# tune2fs -l /dev/ploop43211p1 |grep -i 'block count'
Block count: 52428288
Reserved block count: 2123251
This is still 5%
Let's go back to 100G (shrink):
#vzctl set 9999 --diskspace 100G --save
# tune2fs -l /dev/ploop43211p1 |grep -i 'block count'
Block count: 52428288
Reserved block count: 1310668
Now we're at 20% because that's what's set in /etc/mke2fs.conf. Note
total block count didn't shrink but space inside CT is only 100G.
Beyond this point I'm having trouble finding steps to consistently
recreate the issue but at seemingly random combinations of grow/shrink
when doing the shrinks it will go back to whatever ratio is set in
/etc/mke2fs.conf. This at least shows initially that there is an issue
in the form of an inconsistency.
After the 20% goes into effect, it's also 20% of the total of the max
blocks the image has ever consumed, not 20% of the actual block size.
I'm not sure if this causes any issues inside the CT or not.
/etc/mke2fs.conf should either always be used, or never used.
On 7/17/19 5:20 AM, Igor Sukhih wrote:
On 7/17/19 12:21 PM, Vasily Averin wrote:
Dear Jonathan,
thank you for reporting the problem,
we did no saw such behaviour before.
In fact ploop grow should call resize2fs and probably it ignores reserved ratio
setting.
You can try to run it under strace and look at details, ploop sources are
public available too.
Igor (in cc:) is going to check this behaviour, I hope he will clarify the
situation soon.
Unable to reproduce, resize 10G to 1Tb
10G
Block count: 2620928
Reserved block count: 131046
1TB
Block count: 268434944
Reserved block count: 10763323
Thank you,
Vasily Averin
On 7/16/19 8:15 PM, Jonathan Wright wrote:
What seems to be happening is if you set a reserved_ratio on an image and grow
the image, that ratio is maintained and will stay at that ratio.
When shrinking the image however, mke2fs.conf is referenced and that's the
ratio that gets used.
Is there a reason for this behavior to be inconsistent? I was incorrect about
making new ploop images using mke2fs.conf - it seems they don't - at least not
through vzctl create. It appears to be hard coded at 5%.
On 7/16/19 11:55 AM, Jonathan Wright wrote:
ext4's default 5% reserved ratio is set on ploop images. If you update
/etc/mke2fs.conf and adjust this ratio to say 1%, that's used when the ploop
image is created.
This is great.
When you then resize that image though, the stock 5% is put back in place
instead of the 1% that was on the filesystem (or whatever might be set in
/etc/mke2fs.conf).
Is this intentional functionality for some reason, a bug, or something simple
no one has tried before?
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Jonathan Wright
KnownHost, LLC
https://www.knownhost.com
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