Re: [ovirt-users] oVirt storage best practise

[Yaniv Kaul]

On Wed, Jun 14, 2017 at 4:18 PM, FERNANDO FREDIANI <
fernando.fredi...@upx.com> wrote:

> I normally assume that any performance gain from directlly attaching a LUN
> to a Virtual Machine then using it in the traditional way are so little to
> compensate the extra hassle to do that. I would avoid as much as I cacn use
> it, unless it is for some very special reason where you cannot do in any
> other way. The only real usage for it so far was Microsoft SQL Server
> Clustering requirements.
>

I tend to agree (from performance perspective), though I don't have numbers
to back it up. It probably doesn't matter that much.
There are however other reasons to use a direct LUN - use of storage-side
features, such as replication, QoS, encryption, compression, etc. that you
may wish to apply (or disable) per storage.
Also, there are some strange SCSI commands that some strange applications
need that require direct LUN and SCSI pass-through. Clustering (via SCSI
reservations is certainly the first and foremost but not the only one).
Y.


> Fernando
>
> On 14/06/2017 03:23, Idan Shaby wrote:
>
> Direct luns are disks that are not managed by oVirt. Ovirt communicates
> directly with the lun itself, without any other layer in between (like lvm
> in image disks).
> The advantage of the direct lun is that it should have better performance
> since there's no overhead of another layer in the middle.
> The disadvantage is that you can't take a snapshot of it (when attached to
> a vm, of course), can't make it a part of a template, export it, and in
> general - you don't manage it.
>
>
> Regards,
> Idan
>
> On Mon, Jun 12, 2017 at 10:10 PM, Stefano Bovina  wrote:
>
>> Thank you very much.
>> What about "direct lun" usage and database example?
>>
>>
>> 2017-06-08 16:40 GMT+02:00 Elad Ben Aharon :
>>
>>> Hi,
>>> Answer inline
>>>
>>> On Thu, Jun 8, 2017 at 1:07 PM, Stefano Bovina  wrote:
>>>
 Hi,
 does a storage best practise document for oVirt exist?


 Some examples:

 oVirt allows to extend an existing storage domain: Is it better to keep
 a 1:1 relation between LUN and oVirt storage domain?

>>> What do you mean by 1:1 relation? Between storage domain and the number
>>> of LUNs the domain reside on?
>>>
 If not, is it better to avoid adding LUNs to an already existing
 storage domain?

>>> No problems with storage domain extension.
>>>

 Following the previous questions:

 Is it better to have 1 Big oVirt storage domain or many small oVirt
 storage domains?

>>> Depends on your needs, be aware to the following:
>>> - Each domain has its own metadata which allocates ~5GB of the domain
>>> size.
>>> - Each domain is being constatntly monitored by the system, so large
>>> number of domain can decrease the system performance.
>>> There are also downsides with having big domains, like less flexability
>>>
>>>
 There is a max num VM/disks for storage domain?


 In which case is it better to use "direct attached lun" with respect to
 an image on an oVirt storage domain?

>>>

>>>
 Example:

 Simple web server:   > image
 Large database (simple example):
- root,swap etc: 30GB  > image?
- data disk: 500GB-> (direct or image?)

 Regards,

 Stefano

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Re: [ovirt-users] oVirt storage best practise

[FERNANDO FREDIANI]

I normally assume that any performance gain from directlly attaching a 
LUN to a Virtual Machine then using it in the traditional way are so 
little to compensate the extra hassle to do that. I would avoid as much 
as I cacn use it, unless it is for some very special reason where you 
cannot do in any other way. The only real usage for it so far was 
Microsoft SQL Server Clustering requirements.


Fernando


On 14/06/2017 03:23, Idan Shaby wrote:
Direct luns are disks that are not managed by oVirt. Ovirt 
communicates directly with the lun itself, without any other layer in 
between (like lvm in image disks).
The advantage of the direct lun is that it should have better 
performance since there's no overhead of another layer in the middle.
The disadvantage is that you can't take a snapshot of it (when 
attached to a vm, of course), can't make it a part of a template, 
export it, and in general - you don't manage it.



Regards,
Idan

On Mon, Jun 12, 2017 at 10:10 PM, Stefano Bovina > wrote:


Thank you very much.
What about "direct lun" usage and database example?


2017-06-08 16:40 GMT+02:00 Elad Ben Aharon >:

Hi,
Answer inline

On Thu, Jun 8, 2017 at 1:07 PM, Stefano Bovina
> wrote:

Hi,
does a storage best practise document for oVirt exist?


Some examples:

oVirt allows to extend an existing storage domain: Is it
better to keep a 1:1 relation between LUN and oVirt
storage domain?

What do you mean by 1:1 relation? Between storage domain and
the number of LUNs the domain reside on?

If not, is it better to avoid adding LUNs to an already
existing storage domain?

No problems with storage domain extension.


Following the previous questions:

Is it better to have 1 Big oVirt storage domain or many
small oVirt storage domains?

Depends on your needs, be aware to the following:
- Each domain has its own metadata which allocates ~5GB of the
domain size.
- Each domain is being constatntly monitored by the system, so
large number of domain can decrease the system performance.
There are also downsides with having big domains, like less
flexability

There is a max num VM/disks for storage domain?


In which case is it better to use "direct attached lun"
with respect to an image on an oVirt storage domain?


Example:

Simple web server: > image
Large database (simple example):
   - root,swap etc: 30GB  > image?
   - data disk: 500GB  -> (direct or image?)

Regards,

Stefano

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Re: [ovirt-users] oVirt storage best practise

[Yaniv Kaul]

On Wed, Jun 14, 2017 at 9:23 AM, Idan Shaby  wrote:

> Direct luns are disks that are not managed by oVirt. Ovirt communicates
> directly with the lun itself, without any other layer in between (like lvm
> in image disks).
> The advantage of the direct lun is that it should have better performance
> since there's no overhead of another layer in the middle.
> The disadvantage is that you can't take a snapshot of it (when attached to
> a vm, of course), can't make it a part of a template, export it, and in
> general - you don't manage it.
>

You can, of course, create a snapshot from the storage-side.
Y.


>
> Regards,
> Idan
>
> On Mon, Jun 12, 2017 at 10:10 PM, Stefano Bovina  wrote:
>
>> Thank you very much.
>> What about "direct lun" usage and database example?
>>
>>
>> 2017-06-08 16:40 GMT+02:00 Elad Ben Aharon :
>>
>>> Hi,
>>> Answer inline
>>>
>>> On Thu, Jun 8, 2017 at 1:07 PM, Stefano Bovina  wrote:
>>>
 Hi,
 does a storage best practise document for oVirt exist?


 Some examples:

 oVirt allows to extend an existing storage domain: Is it better to keep
 a 1:1 relation between LUN and oVirt storage domain?

>>> What do you mean by 1:1 relation? Between storage domain and the number
>>> of LUNs the domain reside on?
>>>
 If not, is it better to avoid adding LUNs to an already existing
 storage domain?

>>> No problems with storage domain extension.
>>>

 Following the previous questions:

 Is it better to have 1 Big oVirt storage domain or many small oVirt
 storage domains?

>>> Depends on your needs, be aware to the following:
>>> - Each domain has its own metadata which allocates ~5GB of the domain
>>> size.
>>> - Each domain is being constatntly monitored by the system, so large
>>> number of domain can decrease the system performance.
>>> There are also downsides with having big domains, like less flexability
>>>
>>>
 There is a max num VM/disks for storage domain?


 In which case is it better to use "direct attached lun" with respect to
 an image on an oVirt storage domain?

>>>

>>>
 Example:

 Simple web server:   > image
 Large database (simple example):
- root,swap etc: 30GB  > image?
- data disk: 500GB-> (direct or image?)

 Regards,

 Stefano

 ___
 Users mailing list
 Users@ovirt.org
 http://lists.ovirt.org/mailman/listinfo/users


>>>
>>
>> ___
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>> http://lists.ovirt.org/mailman/listinfo/users
>>
>>
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> Users@ovirt.org
> http://lists.ovirt.org/mailman/listinfo/users
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Re: [ovirt-users] oVirt storage best practise

[Idan Shaby]

Direct luns are disks that are not managed by oVirt. Ovirt communicates
directly with the lun itself, without any other layer in between (like lvm
in image disks).
The advantage of the direct lun is that it should have better performance
since there's no overhead of another layer in the middle.
The disadvantage is that you can't take a snapshot of it (when attached to
a vm, of course), can't make it a part of a template, export it, and in
general - you don't manage it.


Regards,
Idan

On Mon, Jun 12, 2017 at 10:10 PM, Stefano Bovina  wrote:

> Thank you very much.
> What about "direct lun" usage and database example?
>
>
> 2017-06-08 16:40 GMT+02:00 Elad Ben Aharon :
>
>> Hi,
>> Answer inline
>>
>> On Thu, Jun 8, 2017 at 1:07 PM, Stefano Bovina  wrote:
>>
>>> Hi,
>>> does a storage best practise document for oVirt exist?
>>>
>>>
>>> Some examples:
>>>
>>> oVirt allows to extend an existing storage domain: Is it better to keep
>>> a 1:1 relation between LUN and oVirt storage domain?
>>>
>> What do you mean by 1:1 relation? Between storage domain and the number
>> of LUNs the domain reside on?
>>
>>> If not, is it better to avoid adding LUNs to an already existing storage
>>> domain?
>>>
>> No problems with storage domain extension.
>>
>>>
>>> Following the previous questions:
>>>
>>> Is it better to have 1 Big oVirt storage domain or many small oVirt
>>> storage domains?
>>>
>> Depends on your needs, be aware to the following:
>> - Each domain has its own metadata which allocates ~5GB of the domain
>> size.
>> - Each domain is being constatntly monitored by the system, so large
>> number of domain can decrease the system performance.
>> There are also downsides with having big domains, like less flexability
>>
>>> There is a max num VM/disks for storage domain?
>>>
>>>
>>> In which case is it better to use "direct attached lun" with respect to
>>> an image on an oVirt storage domain?
>>>
>>
>>>
>>
>>> Example:
>>>
>>> Simple web server:   > image
>>> Large database (simple example):
>>>- root,swap etc: 30GB  > image?
>>>- data disk: 500GB-> (direct or image?)
>>>
>>> Regards,
>>>
>>> Stefano
>>>
>>> ___
>>> Users mailing list
>>> Users@ovirt.org
>>> http://lists.ovirt.org/mailman/listinfo/users
>>>
>>>
>>
>
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Re: [ovirt-users] oVirt storage best practise

[Luca 'remix_tj' Lorenzetto]

On Thu, Jun 8, 2017 at 4:40 PM, Elad Ben Aharon  wrote:
> Hi,
> Answer inline
>
> On Thu, Jun 8, 2017 at 1:07 PM, Stefano Bovina  wrote:
>>
>> Hi,
>> does a storage best practise document for oVirt exist?
>>
>>
>> Some examples:
>>
>> oVirt allows to extend an existing storage domain: Is it better to keep a
>> 1:1 relation between LUN and oVirt storage domain?
>
> What do you mean by 1:1 relation? Between storage domain and the number of
> LUNs the domain reside on?
>>
>> If not, is it better to avoid adding LUNs to an already existing storage
>> domain?
>
> No problems with storage domain extension.
>>
>>
>> Following the previous questions:
>>
>> Is it better to have 1 Big oVirt storage domain or many small oVirt
>> storage domains?
>
> Depends on your needs, be aware to the following:
> - Each domain has its own metadata which allocates ~5GB of the domain size.
> - Each domain is being constatntly monitored by the system, so large number
> of domain can decrease the system performance.


What do you mean by "reducing system performance"? on hypervisor side
or manager side?

We're planning to move serveral TBs of vm, splitted in several SD of
1TB of size.


Do you suggest creating a big storage domain of several terabytes?
It would be easier also for our deployment scripts, but we're still
valuating if is a good choice.

> There are also downsides with having big domains, like less flexability

Exactly what i was thinking: how do i replace a component of a storage domain?


Luca


-- 
"E' assurdo impiegare gli uomini di intelligenza eccellente per fare
calcoli che potrebbero essere affidati a chiunque se si usassero delle
macchine"
Gottfried Wilhelm von Leibnitz, Filosofo e Matematico (1646-1716)

"Internet è la più grande biblioteca del mondo.
Ma il problema è che i libri sono tutti sparsi sul pavimento"
John Allen Paulos, Matematico (1945-vivente)

Luca 'remix_tj' Lorenzetto, http://www.remixtj.net , 
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Re: [ovirt-users] oVirt storage best practise

[Stefano Bovina]

Thank you very much.
What about "direct lun" usage and database example?


2017-06-08 16:40 GMT+02:00 Elad Ben Aharon :

> Hi,
> Answer inline
>
> On Thu, Jun 8, 2017 at 1:07 PM, Stefano Bovina  wrote:
>
>> Hi,
>> does a storage best practise document for oVirt exist?
>>
>>
>> Some examples:
>>
>> oVirt allows to extend an existing storage domain: Is it better to keep a
>> 1:1 relation between LUN and oVirt storage domain?
>>
> What do you mean by 1:1 relation? Between storage domain and the number of
> LUNs the domain reside on?
>
>> If not, is it better to avoid adding LUNs to an already existing storage
>> domain?
>>
> No problems with storage domain extension.
>
>>
>> Following the previous questions:
>>
>> Is it better to have 1 Big oVirt storage domain or many small oVirt
>> storage domains?
>>
> Depends on your needs, be aware to the following:
> - Each domain has its own metadata which allocates ~5GB of the domain size.
> - Each domain is being constatntly monitored by the system, so large
> number of domain can decrease the system performance.
> There are also downsides with having big domains, like less flexability
>
>> There is a max num VM/disks for storage domain?
>>
>>
>> In which case is it better to use "direct attached lun" with respect to
>> an image on an oVirt storage domain?
>>
>
>>
>
>> Example:
>>
>> Simple web server:   > image
>> Large database (simple example):
>>- root,swap etc: 30GB  > image?
>>- data disk: 500GB-> (direct or image?)
>>
>> Regards,
>>
>> Stefano
>>
>> ___
>> Users mailing list
>> Users@ovirt.org
>> http://lists.ovirt.org/mailman/listinfo/users
>>
>>
>
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Re: [ovirt-users] oVirt storage best practise

[Elad Ben Aharon]

Hi,
Answer inline

On Thu, Jun 8, 2017 at 1:07 PM, Stefano Bovina  wrote:

> Hi,
> does a storage best practise document for oVirt exist?
>
>
> Some examples:
>
> oVirt allows to extend an existing storage domain: Is it better to keep a
> 1:1 relation between LUN and oVirt storage domain?
>
What do you mean by 1:1 relation? Between storage domain and the number of
LUNs the domain reside on?

> If not, is it better to avoid adding LUNs to an already existing storage
> domain?
>
No problems with storage domain extension.

>
> Following the previous questions:
>
> Is it better to have 1 Big oVirt storage domain or many small oVirt
> storage domains?
>
Depends on your needs, be aware to the following:
- Each domain has its own metadata which allocates ~5GB of the domain size.
- Each domain is being constatntly monitored by the system, so large number
of domain can decrease the system performance.
There are also downsides with having big domains, like less flexability

> There is a max num VM/disks for storage domain?
>
>
> In which case is it better to use "direct attached lun" with respect to an
> image on an oVirt storage domain?
>

>

> Example:
>
> Simple web server:   > image
> Large database (simple example):
>- root,swap etc: 30GB  > image?
>- data disk: 500GB-> (direct or image?)
>
> Regards,
>
> Stefano
>
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[ovirt-users] oVirt storage best practise

[Stefano Bovina]

Hi,
does a storage best practise document for oVirt exist?


Some examples:

oVirt allows to extend an existing storage domain: Is it better to keep a
1:1 relation between LUN and oVirt storage domain?
If not, is it better to avoid adding LUNs to an already existing storage
domain?

Following the previous questions:

Is it better to have 1 Big oVirt storage domain or many small oVirt storage
domains?
There is a max num VM/disks for storage domain?


In which case is it better to use "direct attached lun" with respect to an
image on an oVirt storage domain?

Example:

Simple web server:   > image
Large database (simple example):
   - root,swap etc: 30GB  > image?
   - data disk: 500GB-> (direct or image?)

Regards,

Stefano
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