So is it possible to have different filesystem type for some directories under / ,(for example /var and /home as xfs, the rest as ext3 in / ) , without having any problem ?
and the root partition as ext3
Steps to migrate to xfs
Install CentOS, with ext3
Install xfsprogs, xfsdump and a centosplus kernel, to be able to boot with xfs later.
(I don't know what kernel was , but i know was necessary a centosplus one for boot with xfs)
Run the live cd
* Create some directories in /mnt (live cd)
mkdir oldroot newroot oldhome newhome
* mount / and /home in mnt (original ones)
mount -t ext3 /dev/sdb1 /mnt/oldroot
mount -t ext3 /dev/sdb2 /mnt/oldhome
* Mount the new formated partitions in xfs for / and /home
* (supposing you have your centos install in another disk )
* If not rsync all first to another hard drive
mount -t xfs /dev/sda2 /mnt/newroot
mount -t xfs /dev/sda3 /mnt/newhome
* Use Rsync to copy data
(cd /mnt/oldroot/ ; find . -xdev -print0 | rsync -avHx . /mnt/newroot/)
(cd /mnt/oldhome/ ; find . -xdev -print0 | rsync -avHx . /mnt/newhome/)
* compare directories using diff (to be sure all has been copied correctly)
diff -qr /mnt/oldroot/ /mnt/newroot/ > diffroot.log
diff -qr /mnt/oldhome/ /mnt/newhome/ > diffhome.log
* Edit Fstab, Menu.lst
mount --rbind /dev /mnt/newroot/dev
mount --rbind /proc /mnt/newroot/proc
Do this: (without centos doesn't boot)
mkinitrd -v -f image kernel
As to whether you will gain any benefit by having the OS, as well as the data, on xfs partitions I really do not know. I appreciate your argument for doing so but I am not that convinced. Perhaps others will comment?
You won't get much benefit from having / as xfs, and there are a few minor concerns with it.
First of all, depending on your application, you might be better off creating a separate and dedicated partition for holding the data (as opposed to using /home). Something like /opt, or /opt/data.
I definitely wouldn't bother with any kind of wipe and restore to get / as xfs. You're just not going to get any return on that work. Having a filesystem formatted as xfs is only going to be of benefit when working with files on that filesystem.
[font=Verdana]The performance of your application, once it's up and running, is going to be completely independent of what filesystem it was loaded from. In short, leave / alone, or you're wasting your time.[/font]
Additionally, in the even of any disk/partition issues, there are a lot more tools and much better support for ext3 than xfs. In a bad scenario like that, you don't want to be jumping through any more hoops than absolutely necessary to get a box back up and running.
Also, understand that for an average workload, you're only going to see a performance difference of a few percent. There are definitely some (very specific) workloads that will show a significantly bigger performance change, but most won't.
With regards to xfs support and the CentOS Plus kernel, our toracat will be able to comment.
Do these 3D modeling applications install into the /usr? Special apps tend to
lack "proper" rpm-packaging, and when they do, they are better off under some other mount-point.
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