[Users] simfs challenge

[Nick Knutov]

Hello,

One of big reasons to prefer simfs over ploop is disk space overhead in 
ploop after using snapshots (for backups for example).
It can be really huge - we have one CT which takes 120Gb instead of 60Gb 
(df -h inside) after daily backups with vzpbackup (*) tool. It's 
after(!) ploop merge & compact.

Do you plan to make some improvements for this case?

(*) https://github.com/andreasfaerber/vzpbackup

28.01.2016 14:27, Konstantin Khorenko пишет:
> Hi All,
>
> so, this is the current situation with simfs:
>
> First of all we cannot implement as it was previously (in OpenVZ 6, 
> 2.6.32-x kernels).
> This is because there is no vzfs in Virtuozzo 7, but all quota related 
> code used by simfs
> was shared between vzfs and simfs, and maintaining that code for simfs 
> only is definitely
> not the thing we'd be happy to do.
> Yes, we definitely want to reuse some mainstream (or write a 
> mainstream-able) code for it.
>
> So, how this could be implemented?
>
> "Old" simfs fs without quota - is just a bindmount => this is a start 
> point.
> 1st level quota for simfs-based Containers (the quota for the 
> Container as a whole) can be
> implemented using project quota which is going to be accepted to 
> mainstream sooner or later.
>
> As for the 2nd level quota (per-user quota inside a CT), we had not 
> found any good solution
> during our internal discussions, so ideas from community are very 
> welcome.
>
> So what do we have at the moment: you can create a simfs-based 
> Container in Virtuozzo 7
> (see instructions below), but cannot manage quota for it.
>
> What should be done further (that's what you can help us with):
>
> 1. Take project quota kernel patches (which Stas Kinsbursky alredy 
> ported to vz7 kernel
> some time ago), apply them to current vz7 kernel - you'll get the 
> kernel able to manage
> project quota.
>
> 2. Need to add project quota support to appropriate userspace tools: 
> quota-tools and e2fsprogs
> see details at https://bugs.openvz.org/browse/OVZ-6619
>
> Hope that helps to understand our plans on simfs in Virtuozzo 7
> and looking forward for a hero who could drive this forward! :)
>
>
>
> More formal feature description is below:
>
> =========================================================================================== 
>
> 1. Feature
> simfs filesystem for Virtuozzo 7 Containers
>
>
> 2. Description
> https://bugs.openvz.org/browse/OVZ-6613
> https://jira.sw.ru/browse/PSBM-40730
>
> Differences between recommended Containers disk backend (ploop) and 
> simfs:
> https://openvz.org/CT_storage_backends
>
> Unlike previous versions of OpenVZ, simfs layout in Virtuozzo 7 is 
> based on bindmounts.
> This means once you start a simfs-based Container, effectively
> "private" area of a Container is bindmounted to the "root" Container 
> area.
> That's it.
>
> How to create a simfs-based Container:
> * set VEFSTYPE=simfs in the /etc/vz/vz.conf
> # vzctl create $VEID
>
> 3. Products
> Virtuozzo 7, libvzctl-7.0.170
>
>
> 4. Testing
> just a validation:
> - create a Container
> - start/stop the Container
> - destroy the Container
>
> 5. Known issues
> * quota for simfs-based Containers is not implemented
>   - 1st level quota (for the Container as a whole) is planned to be 
> implemented via project quota
>     https://bugs.openvz.org/browse/OVZ-6619
>
>   - 2nd level quota (per-user quota inside a Container) is not planned
>
> * online migration of a simfs-based Container is not implemented
>
>
> 6. Feature owner
> Kernel part:    Stanislav Kinsbursky <skinsbursky at virtuozzo.com>
> Userspace part: Igor Sukhih <igor at virtuozzo.com>
>
>
> -- 
> Best regards,
>
> Konstantin Khorenko,
> Virtuozzo Linux Kernel Team
> _______________________________________________
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> Users at openvz.org
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-- 
Best Regards,
Nick Knutov
http://knutov.com
ICQ: 272873706
Voice: +7-904-84-23-130