[linux-lvm] Size of the mirror log?

[linux-lvm] Size of the mirror log?

[Lupe Christoph]

Hi!

I'm unable to find any information on how the size of the mirror log is
determined. Right now I only have four volumes of 1GB each to test this,
obviously too little. We will be getting a few 128GB volumes soon, but I
would rather have a formula than some test results...

I presume the size will depend on the number of mirror regions, but how
much log does a region require?

Thanks for help,
Lupe Christoph
-- 
| There is no substitute for bad design except worse design.                   |
| /me                                                                          |

Re: [linux-lvm] Size of the mirror log?

[malahal]

Lupe Christoph [lupe@lupe-christoph.de] wrote:
> Hi!
> 
> I'm unable to find any information on how the size of the mirror log is
> determined. Right now I only have four volumes of 1GB each to test this,
> obviously too little. We will be getting a few 128GB volumes soon, but I
> would rather have a formula than some test results...
> 
> I presume the size will depend on the number of mirror regions, but how
> much log does a region require?

Currently the log size is fixed at 1 PE (4MB by default). It is always a
1 PE.

Re: [linux-lvm] Size of the mirror log?

[Milan Broz]

malahal@us.ibm.com wrote:
> Lupe Christoph [lupe@lupe-christoph.de] wrote:
>> I'm unable to find any information on how the size of the mirror log is
>> determined. Right now I only have four volumes of 1GB each to test this,
>> obviously too little. We will be getting a few 128GB volumes soon, but I
>> would rather have a formula than some test results...
>>
>> I presume the size will depend on the number of mirror regions, but how
>> much log does a region require?
> 
> Currently the log size is fixed at 1 PE (4MB by default). It is always a
> 1 PE.

Since LVM2 2.02.44 release mirror log size is properly calculated and can
be higher, it is not fixed to 1 PE anymore.


Milan
--
mbroz@redhat.com

Re: [linux-lvm] Size of the mirror log?

[Alasdair G Kergon]

On Wed, Jan 28, 2009 at 05:56:43PM +0100, Milan Broz wrote:
> malahal@us.ibm.com wrote:
> > Lupe Christoph [lupe@lupe-christoph.de] wrote:
> >> I presume the size will depend on the number of mirror regions, but how
> >> much log does a region require?

An additional region requires an additional 1 bit.

Alasdair
-- 
agk@redhat.com

Re: [linux-lvm] Size of the mirror log?

[malahal]

Milan Broz [mbroz@redhat.com] wrote:
> malahal@us.ibm.com wrote:
> > Lupe Christoph [lupe@lupe-christoph.de] wrote:
> >> I'm unable to find any information on how the size of the mirror log is
> >> determined. Right now I only have four volumes of 1GB each to test this,
> >> obviously too little. We will be getting a few 128GB volumes soon, but I
> >> would rather have a formula than some test results...
> >>
> >> I presume the size will depend on the number of mirror regions, but how
> >> much log does a region require?
> > 
> > Currently the log size is fixed at 1 PE (4MB by default). It is always a
> > 1 PE.
> 
> Since LVM2 2.02.44 release mirror log size is properly calculated and can
> be higher, it is not fixed to 1 PE anymore.
> 
> 
> Milan

Thank you Milan. I was looking at the 2.02.43 that I was working with.

--Malahal.