[ovirt-users] Local and Shared storage in same datacenter

[Pavel Gashev]

I think it's all about online VM migration. oVirt doesn't support online VM migration together with online storage migration. So any storage has to be accessible from any hosts in a datacenter. That's why local storages are too restricted.

Converting Local storages to Shared removes the restriction. Avoiding NFS layer locally removes the NFS performance drawback. And both allow to adhere to the oVirt way.

-----Original Message-----
From: Fernando Frediani <fernando.frediani at upx.com.br>
Date: Monday 31 October 2016 at 17:07
To: Pavel Gashev <Pax at acronis.com>
Subject: Re: [ovirt-users] Local and Shared storage in same datacenter

Why this 'workdaround' to share a local storage as NFS instead os just 
use it as a 'normal' Local storage ? Looks more like a chewing gum.

Is there any work in progress to change the way this storage pool 
manager works ?


On 31/10/2016 12:02, Pavel Gashev wrote:
> Mike,
>
> As workaround it's not very hard to create a mount command wrapper that converts local NFS mounts to bind-mounts. The propper way I think is to patch the VDSM service to handle local NFS mounts. In result, a NFS storage will work like a local storage if it's local.
>
> -----Original Message-----
> From: Mike <maillist at probie.nl>
> Date: Monday 31 October 2016 at 16:33
> To: Pavel Gashev <Pax at acronis.com>, "users at ovirt.org" <users at ovirt.org>
> Subject: Re: [ovirt-users] Local and Shared storage in same datacenter
>
> Hi Pavel,
>
> Op 31-10-2016 om 11:22 schreef Pavel Gashev:
>> Mike,
>>
>> You can share and use your local storage via NFS. So all your storages are shared, and can be used in the same datacenter.
> I installed a nfs server on the hypervisor and am using it that way at
> the moment.
> It feels 'wrong' but it seems to work okay and it is fast as far as I
> can tell.
> Still would like to see another solution without the added latency of
> nfs and be able to utilize directio, etc.
>> -----Original Message-----
>> From: <users-bounces at ovirt.org> on behalf of "Mike (maillinglists)" <maillist at probie.nl>
>> Date: Sunday 30 October 2016 at 13:02
>> To: "users at ovirt.org" <users at ovirt.org>
>> Subject: [ovirt-users] Local and Shared storage in same datacenter
>>
>> Hi guys,
>>
>> There have been a few related questions already that I could find, but I
>> did not find anything relating to my specific use case.
>>
>> Currently it is not possible to mix local storage with shared storage in
>> the same datacenter.
>> The reason seems to be because of the storage pool manager (SPM).
>> This is a role in the datacenter provided to one specific host.
>>
>> While I understand that this makes having local storage impossible, I
>> believe there is a use case to have local storage in a shared storage
>> datacenter.
>> Consider the following:
>> I have a few applications that require 1 milli second latency and at
>> most 2 milli second.
>> That is not consistenly achievable with shared storage, to that end I
>> added flash storage to a few hypervisors.
>> About 5% of my servers require this and are not that resource hungry to
>> require a dedicated physical server.
>> That same 5% also has no requirement to be migrated if a host fails.
>>
>> So in short I have 5 heavy hosts running ovirt with a shared storage
>> domain on NFS for 95% of my servers.
>> All running fine, but I am now unable to run my remaining 5%.
>>
>> To finish up my summary I have been testing various virtualization
>> technologies, like VmWare and Hyper-V.
>> They allow such configurations as I mentioned.
>>
>> I already had some chat on irc with various guys and they suggested that
>> I put this on the mailing list, so here goes.
>>
>> My suggestion would be to evoluate from SPM to SDM.
>> SDM stands for Storage Domain Manager.
>> This would create the possibility to have all nodes in the datacenter
>> participate in the storage handling.
>> A extra benefit would be that local storage could be added.
>>
>> What do you think?
>>
>> Thanks for reading.
>>
>> Kind regards,
>> Mike van Goor
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>>
>
>
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