RAID on Linux with USB devices

Whilst studying for the Linux+ Exam just now, something hit me. If you ever run out of SATA/PATA ports on a system, you could just add more drives on the USB bus. this would be nice for the new RAID5 set up. Granted there’s the physical space/storage issues, but it’s still properly accessible storage. I wonder if mdadm would support the hot-plugability of USB in a RAID array. Hmmm… that would be very cool.

Installing Fedora Core 6 on VMWare Workstation 5.5

When installing Fedora Core 6 on my Windows VMware setup, it failed to find any disks to install on. The reason? I selected the Guest OS as “Red Hat Linux”, seeing as Fedora Core has direct lineaege from Red Hat. Anyway, it doesn’t work and fails to find a disk. To get around this, choose “Red Hat Enterprise Linux 4” or “Other Linux 2.6.x kernel” and it’ll find the Virtual SCSI disk perfectly.

Free Enterprise Search

If you follow this blog, you’ll know that I recently setup an Ubuntu box running Samba with a 2.7TB Raid5 array. Its job is to replace one of our 300GB Dell PowerVault 715N NAS boxes which has become full.

Finding files on our previous 300GB PowerVault was nothing short of a nightmare and, with such a vast amount of data on the new system, we have to ensure that information won’t get ‘lost’ as easily. Obviously proper structuring of directories through a bit of Information Architecture will help, but what we really need is a search facility.

As a small company with a limited budget, the search facility has to be affordable. In addition, it needs to be easily accessible to everyone in the network, preferably without installing extra applications onto client systems…

Remove your domain from AOL’s blacklist

A friend of mine has just had his employer’s Exchange server blacklisted by AOL, meaning anything from or to an aol address won’t go through. This often happens when people mistakenly flag legitimate mail as Spam in their AOL client or you leave your mail server as an Open Relay, opening a nice gateway for spammers.

Check for Open Relay

To check your Mail Server for Open Relay, go here: http://www.checkor.com

If you have an open relay fix it ASAP. You should always enable some kind of authentication on your mail servers! (POP or SMTP auth is usually sufficient)

Remove from AOL Blacklist

To find out how to remove your mail server from the AOL blacklist (and get yourself on their whitelist) check out http://postmaster.aol.com/

RAID-5 in Ubuntu with mdadm

Couldn’t really find anyone who’d documented setting up a RAID 5 array with Linux and mdadm, so figured I’d jot down the method I used in Ubuntu 6.10. It basically boils down to four commands (I am assuming you have a fresh install):

To explain a little:

The first command installs mdadm.

The second command creates the raid array /dev/md0, then sets how many disks – and their respective locations – there’ll be in the array. In my case, we have 5 750GB drives, which are /dev/sda through to /dev/sde. The 1 is the partition identifier. Level sets the raid level, which in this case is raid5.

The third command ‘sudo mke2fs -j /dev/md0 ‘ makes an ext3 filesystem on the array.

And finally ‘sudo mount /dev/md0 /mnt/raid‘ mounts the array to /mnt/raid (you can mount it wherever you like)

Note 1: Make sure you have mdadm installed. If you don’t: sudo apt-get install mdadm

Note 2: If you’re not using Ubuntu, su to root and run the commands without ‘sudo’

Note 3: If you get an error stating ‘mdadm: error opening /dev/md0: No such file or directory’, you need to bypass udev and use this command instead: sudo mdadm --create /dev/md0 --raid-devices=5 /dev/sd[abcde]1 --level=raid5 --auto=yes

Note 4: To view the status of your array: sudo mdadm --detail /dev/md0

Note 5: If you need to view a list of your hard drives, try these commands: ls -l /dev/sd* or ls -l /dev/hd*

I am certainly no Linux expert. Corrections, and suggestions on how to improve this method are encouraged 🙂

Update: There’s a very thorough guide here, but it seems to cover some GUI elements – which wasn’t an option for me.