Re: pitr question

Excuse the ignorance, but I see the following in the docs:

'In any case the hardware architecture must be the same — shipping from,
say, a 32-bit to a 64-bit system will not work.'

Is this specific to the hardware? That is to say, can I use pitr wal
shipping from 64 bit hardware to 64 bit hardware, where one machine is
running a 32 bit OS and the other is running a 64 bit OS?

Further:

Say 32 bit hardware and 64 bit hardware, where both are running a 32 bit OS?

Specifically speaking of RHEL.

Thanks.

--
Until later, Geoffrey

"I predict future happiness for America if they can prevent
the government from wasting the labors of the people under
the pretense of taking care of them."
- Thomas Jefferson

On Wed, Oct 13, 2010 at 11:17 AM, Geoffrey Myers
<lists(at)serioustechnology(dot)com> wrote:
> 'In any case the hardware architecture must be the same — shipping from,
> say, a 32-bit to a 64-bit system will not work.'
>
> Is this specific to the hardware?  That is to say, can I use pitr wal
> shipping from 64 bit hardware to 64 bit hardware, where one machine is
> running a 32 bit OS and the other is running a 64 bit OS?
>

It applies to the OS. The OS determines the sizes of integers,
padding alignment, etc. Running 32-bit OS on an amd64 class processor
is the same as running it on a x86 class processor. Other processors
(such as PowerPC) may behave differently, I don't know.

On 10/13/2010 11:30 AM, zhong ming wu wrote:
> On Wed, Oct 13, 2010 at 11:17 AM, Geoffrey Myers
> <lists(at)serioustechnology(dot)com <mailto:lists(at)serioustechnology(dot)com>> wrote:
> > Excuse the ignorance, but I see the following in the docs:
> >
> > 'In any case the hardware architecture must be the same — shipping from,
> > say, a 32-bit to a 64-bit system will not work.'
>
> postgres only sees the OS. It does not care what hardware you got. So
> you must use the same type of OS: both 32 bit or both 64 bit.

As I expected, thus the document should possibly be rephrased to
indicate it's the OS not the physical hardware that is the issue.

--
Until later, Geoffrey

"I predict future happiness for America if they can prevent
the government from wasting the labors of the people under
the pretense of taking care of them."
- Thomas Jefferson

Vick Khera <vivek(at)khera(dot)org> writes:
> On Wed, Oct 13, 2010 at 11:17 AM, Geoffrey Myers
> <lists(at)serioustechnology(dot)com> wrote:
>>> 'In any case the hardware architecture must be the same shipping from,
>>> say, a 32-bit to a 64-bit system will not work.'

>> Is this specific to the hardware? That is to say, can I use pitr wal
>> shipping from 64 bit hardware to 64 bit hardware, where one machine is
>> running a 32 bit OS and the other is running a 64 bit OS?

> It applies to the OS. The OS determines the sizes of integers,
> padding alignment, etc. Running 32-bit OS on an amd64 class processor
> is the same as running it on a x86 class processor. Other processors
> (such as PowerPC) may behave differently, I don't know.

It's not really the OS but the build of Postgres. Most 64-bit OSes are
perfectly capable of running 32-bit executables. You can ship WAL from
one machine running a 32-bit Postgres executable to another one running
a 32-bit executable (of the same hardware architecture), regardless of
whether the hardware or the OS is 64-bit-capable on either end. But you
can't ship WAL between 32-bit and 64-bit executables.

regards, tom lane

On Wed, 2010-10-13 at 11:40 -0400, Geoffrey Myers wrote:
> On 10/13/2010 11:30 AM, zhong ming wu wrote:
> > On Wed, Oct 13, 2010 at 11:17 AM, Geoffrey Myers
> > <lists(at)serioustechnology(dot)com <mailto:lists(at)serioustechnology(dot)com>> wrote:
> > > Excuse the ignorance, but I see the following in the docs:
> > >
> > > 'In any case the hardware architecture must be the same — shipping from,
> > > say, a 32-bit to a 64-bit system will not work.'
> >
> > postgres only sees the OS. It does not care what hardware you got. So
> > you must use the same type of OS: both 32 bit or both 64 bit.
>
> As I expected, thus the document should possibly be rephrased to
> indicate it's the OS not the physical hardware that is the issue.

No. Because PostgreSQL itself must also be the same architecture.

Joshua D. Drake

--
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On 14/10/10 00:18, Joshua D. Drake wrote:
> On Wed, 2010-10-13 at 11:40 -0400, Geoffrey Myers wrote:
>> On 10/13/2010 11:30 AM, zhong ming wu wrote:
>>> On Wed, Oct 13, 2010 at 11:17 AM, Geoffrey Myers
>>> <lists(at)serioustechnology(dot)com <mailto:lists(at)serioustechnology(dot)com>> wrote:
>>> > Excuse the ignorance, but I see the following in the docs:
>>> >
>>> > 'In any case the hardware architecture must be the same — shipping from,
>>> > say, a 32-bit to a 64-bit system will not work.'
>>>
>>> postgres only sees the OS. It does not care what hardware you got. So
>>> you must use the same type of OS: both 32 bit or both 64 bit.
>>
>> As I expected, thus the document should possibly be rephrased to
>> indicate it's the OS not the physical hardware that is the issue.
>
> No. Because PostgreSQL itself must also be the same architecture.

No it doesn't. As Tom Lane pointed out, plenty plenty of 64-bit OSes on
64-bit hardware will run 32-bit binaries. Additionally, most 64-bit
hardware will run 32-bit OSes with 32-bit binaries.

So long as Pg has the same word sizes, endianness, etc, it won't care.
This means that you can't log-ship from 32-bit Intel to 32-bit
big-endian PPC and expect it to work, but you can log-ship from 32-bit
Pg running on 64-bit Intel to 32-bit Pg running on 32-bit Intel and
that'll be fine.

--
Craig Ringer

Tech-related writing: http://soapyfrogs.blogspot.com/