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Do I really need 64 bit linux?
wheel




msg:4395019
 2:52 am on Dec 7, 2011 (gmt 0)

I'm migrating to a new server, dual CPU's with 8 cores each, 16 gigs ram, the whole shebang.

Current server is 32 bit linux.

Trying to migrate to 64 bit linux (i.e. installing that as the base, then moving software up to the new platform). Getting all sorts of headaches that I suspect have to do with the change in platform.

Does 64 bit really matter than much? I want the horsepower out of this machine over the long term, but maybe this isn't worth the headaches.

Or what about if I started off with 32 bit, then did an upgrade of the OS, is that likely to work?

 

Leosghost




msg:4395029
 3:34 am on Dec 7, 2011 (gmt 0)

Not much point in putting in ( and paying for ) 16 gigs of RAM if the 32 bit OS can't talk with all of it :)

32 bit is going to be able to see and talk with, a little short of 4 gigs..

IIWY I'd get 64 bit system set up from the start.."clean" install is always better than "upgrade"..

[edited by: Leosghost at 3:40 am (utc) on Dec 7, 2011]

incrediBILL




msg:4395030
 3:39 am on Dec 7, 2011 (gmt 0)

Does 64 bit really matter than much?


It does if you want to actually use all that RAM

Or what about if I started off with 32 bit, then did an upgrade of the OS, is that likely to work?


Waste of time.

Either do it or don't.

I've been running RHE 64-bit for a few years now, worked fine first time out of the box.

Never looked back.

Leosghost




msg:4395031
 3:43 am on Dec 7, 2011 (gmt 0)

@wheel..what flavour are you on now in 32 ..and what flavour are you looking at in 64 ?

lammert




msg:4395104
 9:27 am on Dec 7, 2011 (gmt 0)

64 bit compiled applications use more memory than their 32 bit versions, mainly because code and data structures are aligned in blocks of 8 bytes rather than 4 bytes. Expect an average increase of your application footprint around 20%. So if you need 1GB for a running application on a 32 bit box, expect the same application with the same load to use around 1.25GB on a 64 bit platform.

Furthermore a number of applications are more buggy on 64 bit than on 32 bit, although they seem to work. This is often caused by long/int conversions because these type definitions on C/C++ changed slightly between the two platforms. One such a problem child I have found is the ntpd time server which produces false statistics on 64 bit in a number of distributions.

Some applications are not able to share data between 32 and 64 bit. AWStats data files collected on 32 bit Linux can't be moved to a 64 bit Linux machine for example.

But having said that, 64 bits gives you a lot of extra memory space if you have installed the RAM and it provides a growth path to the future. I am currently running three 32 bit Linux servers and two 64 bit servers and planning to upgrade them all to 64 bit in the near future.

tangor




msg:4395119
 10:22 am on Dec 7, 2011 (gmt 0)

Another way of looking at it is endure the pain now, or at a later time. Move to 64bit was done some time back. There's a reason why it is called the bleeding edge of technology.

Frank_Rizzo




msg:4395122
 10:40 am on Dec 7, 2011 (gmt 0)

When I moved to 64 bit a couple of years ago I ran a few tests to see which was faster.

32-bit passed all tests as the fastests but obviously there is the 4Gb limit - which is going to be useless if you are running a meaty DB.

You want the O/S and apps to use the RAM for caching, buffers and stuff. Thus for any rig with > 4Gb you are better off with 64-bit.

One alternative is 32-bit in PAE mode. This allows 32-bit to break the 4Gb barrier. But there is a slight performance hit with this.

---

As the others have said you are better off doing a fresh install with 64-bit version.

One gotcha with Centos 64-bit is that you can get into a mess with it installing some 32-bit apps and some 64-bit. In yum.conf put

exclude = *.i?86

right at the start, before you do any further yum install / yum updates

apachewebserverguy




msg:4417718
 3:09 am on Feb 15, 2012 (gmt 0)

Yes, with 16gb of memory, the 32-bit linux os is not utilizing any but 3gb of it.

zaktoo




msg:4437011
 10:35 am on Apr 4, 2012 (gmt 0)

@apachewebserverguy Only if you have done nothing to enable it to do so. Google PAE.

zaktoo




msg:4437012
 10:37 am on Apr 4, 2012 (gmt 0)

As far as I'm concerned, there's no issue with going 64 bit. Linux has been 64 bit friendly almost since the get-go. I have had absolutely no issues running 64 bit for the last 6+ years.

lammert




msg:4437013
 10:44 am on Apr 4, 2012 (gmt 0)

Welcome here on WebmasterWorld zaktoo and thanks for your insights. With 6+ years of experience, you are certainly one of the early users of 64 bit Linux and have a wealth of experience.

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