[TriLUG] Department server sonfig suggestions please.

[Matthew Lavigne]

On Tue, 03 Aug 2004 21:32:27 -0400, David A. Cafaro <dac at trilug.org> wrote:
> On Tue, 2004-08-03 at 16:19, bp wrote:
> <snip>
> > 2) How does linux software RAID5 work for dissimilarly size SOFTWARE RAID
> > slices? See sdb vs. the rest of / members.
> 
> Last I checked it doesn't, each member partition of a RAID5 system needs
> to be the same size.  So you would have to loose 1.5GB on each disk
> after sdb based on your layout.
 
I disagree with you here, if you are doing RAID5 in HW (really the
only place to do it).  You use all the disks to make 1 large Raid 5
Disk that is usually equal to disk size x4 and you partition that. 
Therefore the OS only sees an sda.  I have that with a system that is
sda - sde.  Each drive is a Raid5 device and the OS sees it as a drive
 Example:

[lavigne at avtestsvr lavigne]$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             1.4G  415M  986M  30% /
/dev/sda2              43G   38G  3.6G  92% /home
/dev/sda3             6.2G  2.0G  3.9G  34% /usr
/dev/sda5             5.8G   53M  5.4G   1% /tmp
/dev/sda6             3.4G  334M  2.8G  11% /var
/dev/sda7             2.9G  195M  2.5G   7% /opt
/dev/sdb1              67G   64G     0 100% /ISOs
/dev/sdc1             133G   73G   54G  58% /storage
/dev/sdc2             133G   72G   54G  57% /mnt/sdc2
/dev/sdd1             133G   51G   75G  41% /builddrive
/dev/sdd2             133G   95G   31G  75% /mnt/sdd2
/dev/sde1             367G  130G  218G  38% /images
[lavigne at avtestsvr lavigne]$


> In my world it's always nice to run the OS on RAID5 if you have the
> option.  Remember that it's not just the down time to reinstall the OS.
> On RAID5 the system isn't going to stop running when a disk fails (it
> will slow down).  You can even put the /boot on the raid, and with some
> carefull grub in MBR setup you can even make sure that your system
> always reboots even with a failed disk.  Of course this is all about
> making the system hard to knock down.

I agree completely here.  The setup above has been up an running for
over 18 months with a total of 9 disk failures in that time (great
thing about developmental hard disks) and I have never lost the OS or
data. (Knock on wood).

Matthew