10:22 a.m.
Is there any reason anyone can think of why we would need to specify a
specific storage domain for a VM to use when it hibernates? Ideally we
could just grab any storage domain that has space and use it for
hibernation (as long a we remember where we did it!).
thoughts?
11:46 a.m.
On 12/12/2011 19:22, Jon Choate wrote:
Is there any reason anyone can think of why we would need to specify
a
specific storage domain for a VM to use when it hibernates? Ideally
we could just grab any storage domain that has space and use it for
hibernation (as long a we remember where we did it!).
thoughts?
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Probably for the same reason we enforce all VMs disks to be on the same
storage domain. Habit.
But I also think it make sense, for the hibernation file to be in the
same SD as the system disk. There's also a higher chance that domain
will be online and available to the host.
Y.
12:04 p.m.
On 12/12/2011 01:46 PM, Yaniv Kaul wrote:
On 12/12/2011 19:22, Jon Choate wrote:
> Is there any reason anyone can think of why we would need to specify
> a specific storage domain for a VM to use when it hibernates?
> Ideally we could just grab any storage domain that has space and use
> it for hibernation (as long a we remember where we did it!).
>
> thoughts?
> _______________________________________________
> Engine-devel mailing list
> Engine-devel(a)ovirt.org
> http://lists.ovirt.org/mailman/listinfo/engine-devel
Probably for the same reason we enforce all VMs disks to be on the
same storage domain. Habit.
Eliminating this dependency would be part of the
feature to allow VMs to
have their disks on multiple storage domains.
But I also think it make sense, for the hibernation file to be in the
same SD as the system disk. There's also a higher chance that domain
will be online and available to the host.
Y.
Is it possible for ovirt-engine to identify which disk is the system disk?
What should the algorithm be for determining a storage domain to
hibernate a diskless VM?
It seems like things would be simplified if we did not restrict
ourselves and could use any available storage domain regardless of
whether the vm has disks or not.
12:10 p.m.
On 12/12/2011 21:04, Jon Choate wrote:
On 12/12/2011 01:46 PM, Yaniv Kaul wrote:
> On 12/12/2011 19:22, Jon Choate wrote:
>> Is there any reason anyone can think of why we would need to specify
>> a specific storage domain for a VM to use when it hibernates?
>> Ideally we could just grab any storage domain that has space and use
>> it for hibernation (as long a we remember where we did it!).
>>
>> thoughts?
>> _______________________________________________
>> Engine-devel mailing list
>> Engine-devel(a)ovirt.org
>> http://lists.ovirt.org/mailman/listinfo/engine-devel
>
> Probably for the same reason we enforce all VMs disks to be on the
> same storage domain. Habit.
Eliminating this dependency would be part of the feature to allow VMs
to have their disks on multiple storage domains.
> But I also think it make sense, for the hibernation file to be in the
> same SD as the system disk. There's also a higher chance that domain
> will be online and available to the host.
> Y.
Is it possible for ovirt-engine to identify which disk is the system
disk?
In several ways:
1. Guess.
2. The first
3. Use the one with the 'Is Bootable' flag.
Y.
What should the algorithm be for determining a storage domain to
hibernate a diskless VM?
None, we should only support S4 and say farewell to the external
hibernation. I don't think there is a good enough reason to keep it
(Ayal might disagree, but I disagree with his reasons).
It seems like things would be simplified if we did not restrict
ourselves and could use any available storage domain regardless of
whether the vm has disks or not.
Perhaps. What's the real benefit, except of freedom of choice? I
personally would look at compressing that hibernation file, btw. Always
annoyed me the size of it, and I expect fast compression to enable
faster suspend-resume cycles. I believe libvirt support some compression
methods.
Y.
1:31 p.m.
On 12/12/2011 02:10 PM, Yaniv Kaul wrote:
On 12/12/2011 21:04, Jon Choate wrote:
> On 12/12/2011 01:46 PM, Yaniv Kaul wrote:
>> On 12/12/2011 19:22, Jon Choate wrote:
>>> Is there any reason anyone can think of why we would need to
>>> specify a specific storage domain for a VM to use when it
>>> hibernates? Ideally we could just grab any storage domain that has
>>> space and use it for hibernation (as long a we remember where we
>>> did it!).
>>>
>>> thoughts?
>>> _______________________________________________
>>> Engine-devel mailing list
>>> Engine-devel(a)ovirt.org
>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
>>
>> Probably for the same reason we enforce all VMs disks to be on the
>> same storage domain. Habit.
> Eliminating this dependency would be part of the feature to allow VMs
> to have their disks on multiple storage domains.
>> But I also think it make sense, for the hibernation file to be in
>> the same SD as the system disk. There's also a higher chance that
>> domain will be online and available to the host.
>> Y.
> Is it possible for ovirt-engine to identify which disk is the system
> disk?
In several ways:
1. Guess.
2. The first
3. Use the one with the 'Is Bootable' flag.
Those all seem to have the
possibility of getting the wrong disk. If
the cost of getting the wrong disk is low anyway then I would argue that
we don't need to find the system disk and we could hibernate alongside
any disk.
Y.
>
> What should the algorithm be for determining a storage domain to
> hibernate a diskless VM?
None, we should only support S4 and say farewell to the external
hibernation. I don't think there is a good enough reason to keep it
(Ayal might disagree, but I disagree with his reasons).
>
> It seems like things would be simplified if we did not restrict
> ourselves and could use any available storage domain regardless of
> whether the vm has disks or not.
Perhaps. What's the real benefit, except of freedom of choice? I
personally would look at compressing that hibernation file, btw.
Always annoyed me the size of it, and I expect fast compression to
enable faster suspend-resume cycles. I believe libvirt support some
compression methods.
Y.
The benefit is that we have one code path for hibernation. The user
likely doesn't understand what happens during hibernation and likely
doesn't care where the data is stored so we should choose the easiest
path for us to implement. My (perhaps naive) assumption is that all
storage domains are just as reliable and choosing one randomly will not
be any worse than any algorithm we could design.
2:20 p.m.
On 12/12/2011 10:31 PM, Jon Choate wrote:
On 12/12/2011 02:10 PM, Yaniv Kaul wrote:
> On 12/12/2011 21:04, Jon Choate wrote:
>> On 12/12/2011 01:46 PM, Yaniv Kaul wrote:
>>> On 12/12/2011 19:22, Jon Choate wrote:
>>>> Is there any reason anyone can think of why we would need to
>>>> specify a specific storage domain for a VM to use when it
>>>> hibernates? Ideally we could just grab any storage domain that has
>>>> space and use it for hibernation (as long a we remember where we
>>>> did it!).
>>>>
>>>> thoughts?
>>>> _______________________________________________
>>>> Engine-devel mailing list
>>>> Engine-devel(a)ovirt.org
>>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
>>>
>>> Probably for the same reason we enforce all VMs disks to be on the
>>> same storage domain. Habit.
>> Eliminating this dependency would be part of the feature to allow VMs
>> to have their disks on multiple storage domains.
>>> But I also think it make sense, for the hibernation file to be in
>>> the same SD as the system disk. There's also a higher chance that
>>> domain will be online and available to the host.
>>> Y.
>> Is it possible for ovirt-engine to identify which disk is the system
>> disk?
>
> In several ways:
> 1. Guess.
> 2. The first
> 3. Use the one with the 'Is Bootable' flag.
Those all seem to have the possibility of getting the wrong disk. If the
cost of getting the wrong disk is low anyway then I would argue that we
don't need to find the system disk and we could hibernate alongside any
disk.
1. how about KISS and choose the disk the user flagged as type = system
(the field already exists and is used today. iirc, backend doesn't even
allow choosing more than one, etc.)
2. diskless VMs - fail the operation. it would fail if you try to
hibernate from inside the guest as well (S4) which are considering
moving to.
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5 comments
3 participants
participants (3)
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Itamar Heim -
Jon Choate -
Yaniv Kaul