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[CentOS] Partition/filesystem expansion difficulties

Hugh E Cruickshank
Mar 17, 2008 at 3:55 am
CentOS 4.6

Hi All:

I am now officially stumped. I have tried everything that can think
of and I have googled until I am blue in the face and tried just
about everything that I could find that looked the least bit like it
might apply and still no (or at least partial) joy. I am going to
cram as much information into this email as I can and hope that
someone out there can either tell me what I am doing wrong or
point me in a new direction for research.

The hardware:

We have an Acer G700 server which comes with 8 internal hot swap SCSI
bays connected to an Adaptec SCSI HBA. There are two banks of 4
drives connect to each of the two channels of the Adaptec HBA. To
this we have added an IBM EXP400 external array with 12 hot swap SCSI
drives connected to an LSI MegaRAID HBA. 36GB drives were used
throughout. The external drives were configured as 6 mirror pairs
through the MegaRAID BIOS.

The OS install:

When I installed CentOS 4 originally I allowed the installer to
configure the 8 internal drives with software mirroring and the
external drives as a striped set effectively making the external disk
array a RAID 10 array.

The original problem:

Our boot drive failed which did not cause an immediate problem as the
system kept on running. The real problem was that I had already used
all the spare drives I had on-hand and I could not source a replacement
drive that matched on size and speed (10K).

The original solution:

I then had what I thought was a good idea and I purchase three 146GB
10K drives. I would replace the two 36GB drives used in the system
mirrored pair with 146GB drives and have one 146GB spare. I would
then be able to free up a 36GB to use as a spare for the other three
pairs of drives. This proved to be easier said then done but I did
eventually get it done by using Norton Ghost to copy the good mirrored
36GB drive on to two of the 146GB drives and then using grub to install
the bootloader (which I found out the hard way is NOT installed on the
mirrored drive - ARGHHHHHH!). However I did get it done but with one minor
problem.

The current problem:

The two 146GB drives are now partitioned as 36GB and I want to expand
the partitions and the installed filesystems to use the additional
space available on the drives. The current partition looked like:

Device Boot Start End Blocks Id System
/dev/sda1 * 1 64 514048+ fd Linux raid autodetect
/dev/sda2 65 1084 8193150 fd Linux raid autodetect
/dev/sda3 1085 1339 2048287+ fd Linux raid autodetect
/dev/sda4 1340 4462 25085466 f W95 Ext'd (LBA)
/dev/sda5 1340 4462 25085466 fd Linux raid autodetect

No problem I thought and proceeded make a Ghost copy of the boot drive
and then used PartedMagic to expand both the last physical and logical
partitions and the resident ext3 files system. Lucky thing I mad that
Ghost copy and the filesystem turned out to be corrupt (could not find
the super block). Restored from the backup.

I then tried using PartedMagic to expanding just the last physical
partition and that worked. The current fdisk for both sda and sde looks
like:

Device Boot Start End Blocks Id System
/dev/sda1 * 1 64 514048+ fd Linux raid autodetect
/dev/sda2 65 1084 8193150 fd Linux raid autodetect
/dev/sda3 1085 1339 2048287+ fd Linux raid autodetect
/dev/sda4 1340 17849 132616575 f W95 Ext'd (LBA)
/dev/sda5 1340 4462 25085466 fd Linux raid autodetect

I then tried to use resize2fs to expand the files systems but that
did on work. No error, it just report that the filesystems were
already at the full size.

Today I tried to use:
mdadm --grow /dev/md3 --size=max
resize2fs /dev/md3
but again no joy (md3 is the filesystem in sda5/sde5). No errors but
no change either.

I even thought to look at LVM but, as far as I can tell, that is not
being used in our case (all drives are listed and unregistered).

The plea:

If anyone has any thoughts on what I have been doing wrong or a new
direction that I can research I would really appreciate it. From
everything that I have read this should be doable. My next step is
to backup the contents of the filesystem and then delete it, re-create
it and restore the backup. If that is the only way of doing this then
I will gladly do it but I still think I should be able to expand it
in-place (just call me stubborn).

TIA

Regards, Hugh

--
Hugh E Cruickshank, Forward Software, www.forward-software.com
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