| Re: ploop and trim/ discard support [message #47824 is a reply to message #47822] |
Thu, 13 September 2012 07:22   |
Kirill Korotaev
Messages: 137
Registered: January 2006
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Senior Member |
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On Sep 13, 2012, at 01:38 , Corin Langosch wrote:
>
> On 12.09.2012 at 21:34 +0200, Kir Kolyshkin <kir@openvz.org> wrote:
>> On Sep 12, 2012 11:20 PM, "Corin Langosch" <info@corinlangosch.com> wrote:
>> >
>> > Hi,
>> >
>> > it seems that when creating & deleting files inside a ploop backed container the backing image file doesn't shrink. So the image file is still consuming around 400 GB, while in the container df shows only 100 GB in use.
>> >
>> > ll on host: -rw------- 1 root root 384G Sep 12 21:06 root.hdd
>> > df on container: /dev/ploop1 493G 103G 390G 21% /
>>
>> We have online shrink. It's "ploop balloon discard" or just "vzctl compact". You'd better have ploop and vzctl from git (both are really close to be released).
>>
>
> The system's still working heavily but the image is already reduced by around 60 GB so it seems to work well. :)
>
> Would you suggest putting some script into crontab to compact all ploop images ex. once a week? Or probably do something like ctid%7 and compact a few of them every night?
>
> BTW: the man of vzctl contains the "compact" command. But the usage output of vzctl doesn't. Shall I file a bug report for it?
>
> BTW 2: I just read about the ploop ballooning technique in the wiki. Am I correct in that it works quite similar to sdelete on windows ( http://pastie.org/4710364 or http://technet.microsoft.com/en-us/sysinternals/bb897443.asp x)?
No, AFAIR we should use TRIM on ext4 and it simply reports unused space.
Balloon is used for "resize" via allocating some space and hiding it from user, but for compacting it's a bit bad since can cause ENOSPC while it's really not...
Kirill
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