Re: [gentoo-user] Moving / around...

[meino.cramer@gmx.de]

Alex Schuster <wonko@wonkology.org> [10-09-12 04:13]:
> meino.cramer@gmx.de writes:
> 
> > I think there is some misunderstanding:
> > 
> > Before migration to 64bit:
> > 
> > /dev/sda3 is mounted on / and contains the 32bit Gentoo
> > 
> > /dev/sda10 is mounted on /home/mcc/migration and will contain the
> > stuff of the 64bit Gentoo
> > 
> > After migration I will *not* mount /dev/sda10 on / but will clear all
> > stuff from /dev/sda3 and move the contents from /dev/sda10 to
> > /dev/sda3.
> > 
> > Is still valid what you said under this premissions, Wonko?
> 
> That's how I understood it, although I assumed the temproary 64bit install 
> would be on a 2nd drive, thus you would copy it back once it seems to 
> work. No, I see no problem with this.
> 
> About performance: I'm not sure it will be even noticeable. Yes, most 
> drives (but not all) are organized so the first partitions go to the 
> outside, which is faster. With LVM, I used to create two volume groups on 
> my drive, a group for swap and the system, and another one for data. But 
> then I thought it's not worth the effort, and I lose some of the LVM 
> benefits. Well, with everything encrypted I don't get full performance 
> anyway, so my case might be a little different.
> 
> But the performance increase is only true when reading lots of data. I'm 
> not sure how big the role of this is in real life. Access time is not 
> influenced, it will on average take half a turn of the drive till the 
> heads can access the data, and to me it looks like typical stuff a linux 
> system does is reading many not so large files, cluttered around in the 
> file system. But that's my guess only. And I understand that you like to 
> optimize stuff - I like to do this too. But sometimes I think that the 
> potential benefit might not be so large, compared to the time I spend 
> moving data around to the ideal place, or the time I would need to spend 
> thinking about how to tune things. Or the time you need to fix a problem 
> that you know was working in the old system, but this is gone now and you 
> cannot have a quick look at it, or just boot into it. You lose the 
> opportunity to start your old system in order to compare the times of your 
> big renderings. And maybe at one point you need to create some true 32bit 
> applications? Happened to me. So I just chroot into my old system and 
> build there.
> 
> Oh, and you mentioned databases. Yes, mysql stores itsa data in machine-
> depenent form. You will need to dump the data and re-import it in the new 
> system. You will be happy to still have the 32bit system in such a case :)
> 
> 	Wonko
> 

I also cannot evaluate the real impact the position of the /-partition
on the harddisk has on system performance. I read about it years ago
and since than I always put the partitions always in the sequence of
"boot","swap","root","home" onto the harddisks. May be its only a
tradition nowadays... ;)

Do you know of any other kind of data beside databses, which may be
machinedependant or cause trouble while migrating to 64bit?

Best regards,
mcc