Expanding RAID5 guidance

christian.peper at kpn.com christian.peper at kpn.com
Mon Feb 2 05:06:19 CST 2009


I'll try to help out some :) 

> -----Original Message-----
[schnipp]
> Proposed Objective:
>    Add 2 - 36GB drives in remaining spare slots
>    Expand Raid5 to include the added space
>    Make use of the added space by users of the file server
> 
> I know the first rule of thumb with managing raids and file 
> systems is to have good backups (multiple backups are better).

Excellent! If you can shutdown the server, doing a 'dd' or using another
tool grap disk images and store them for safekeeing may help in a worst
case scenario.
 
> and I am writing up a detailed list of additional files to 
> backup besides my home and data directories, so I think I 
> have this covered.  My second task has been to make sure that 
> I have a rescue disk or reinstallation disks available in 
> case its needed.  If OS installation becomes necessary for 
> some reason I am considering upgrading to 5.2 (but that is 
> beside the point).
If you do, PLEASE do yourself a favor and use LVM that time! :)

> 1.  How long does the reconfiguration process take (I will do 
> this on a weekend when no one is using the system)?
Don't know for sure, but I'd expect a few hours in the Dell PERC
console. I played with this once on a low-end server it took like an
hour to resize the RAID5 volume. So I'm guestimating 2-4 hours.

> 2.  How do I know when the reconfiguration process is done 
Resize RAID5 array
Boot LiveCD (otherwise you can't unmount any used system partitions)
Fsck all paritions to be sure their healthy
Partition new space in RAID array (fdisk /dev/sda)
Format ecosystem2
Copy content from /ecosystem to ecosystem2
Adjust fstab
Format usr2
Copy content from /usr to /usr2
Adjust fstab
Repeat until done

> Linux-based Servers, Feb. 2003) it appears that I will need 
> to expand the file system to use the new space; 
You can only resize a filesystem if there is room inside a partition. I
think in yhour case there is not. So that's why I suggest creating new
partitions and copying old contents over one by one.

> 3.  What are the general steps that I need to do after my 
> raid reconfiguration is complete to achieve my general objective?

See above

> 4.  Would it be possible to add the new space to one or two 
> existing partitions?  I am thinking sda2 and sda10 
> (/ecosystem is our samba share data directory that would be 
> given 90% of the new space).

Generally no, that's what LVM is for.

> 5.  Will I need to add/create a new partition (and samba 
> mount point) to make use of the new space?  If so I could 
> reorganize our data files to make use of two samba mount points.

Not necessarily. I'd create a new bigger partition for samba, copy
contents over and adjust the mount points.

> 6.  Any other pitfalls I should be aware of, such as what 
> steps need to be done on unmounted drives?

If it's just a samba server and not more, try to reinstall the server
using LVM and restore the data from a backup. If it's just home dirs and
the share, all you mainly need to do is make sure users retain their uid
and gui! Otherwise they won't be owners anymore. If you have MS AD or
LDAP, this will be trivial.

Chris.



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