Linux Software Raid Notes – Replacing Drives



This post is going to be somewhat of a “link dump” for me of some pages that I’ve been perusing lately. After playing with RT (request tracker) – I added a few ticket items for the home network. Now, if you’ve been a longtime reader and sorted through ALL of these posts here you’ll know that I’ve made use of software raid on the home systems. Why? Linux software raid seems fairly reliable (so far – 2 years +). It doesn’t depend on a specific piece of hardware. In short IF the worst happens and the array fails I should be able to retrieve data from an individual drive more easily than if it were hardware raid. I’m using Raid Level 1 (cloning/mirroring) and ext3 is the filesystem on top. I’ve had some slight problems with one drive in both the Desktop and server arrays and both arrays had been degraded for some time. My goal was ultimately redundancy and to eliminate the disruption that hard drive failures have given over the last few years.


When push comes to shove I’m cheap and hadn’t looked at replacing the drives yet. (Potentially a problem especially since I was down to 1 drive for 2 out of 3 arrays.) So, I was running a risk for several months. The main reasons I’ve procrastinated is 1) I’m cheap and 2) I’m busy. The other reason though is the two arrays were made of 400gb sata drives which are now hard to find. 500 gb is the new standard size. Now, I don’t want to waste space so… it’s been a bit of a mental puzzle thinking about replacing one, growing the partition size and then replacing the other to pass along to the second system.

So….. long story short. I was able to re-add the drives to their respective arrays after researching the best way to grow a mirrored array onto larger devices. Why? When the arrays degraded they did so for pending sector reads. I’ve tested the drives via smart and they seem okay. So, I tried re-adding and so far all seems good.

Anyway, here’s the link dump:

Good reminder – http://www.freddenny.com/UNIX/linuxRAID.html – making raid volumes bootable when moved.

Resizing a raid 1 system partition – http://mkfblog.blogspot.com/2007/11/resizing-raid1-system-partition.html

Looks like gparted supports software raid now – http://gparted.sourceforge.net/news.php

Just some notes for a reminder.

RAID is not a substitute for backups. If you accidentally delete a file, it’s still GONE. If you have corruption on one drive (or via the bus) your data is still GONE. Schedule backups of important data.

In sum – replacing drives in a software raid array is quite simple – especially if they’re the same size. Moving to larger drives and not wasting space is a bit more complicated and is a bridge I’ll have to cross at some point.

As a side note, I discovered that I had two more drives of equal size (2 160GB drives) in one system that I had originally intended to mirror those as well, but they needed data cleanup. I spent some time cleaning up the data on one then deleted it’s partitions – created a new partition of the linux auto raid type and create a new raid device with that drive and a missing drive. After that, I created the ext3 filesystem and moved the files over from the other drive. Then I blew away the partition on the 2nd drive and re-partitioned that to be a linux auto raid partition. Then I added it to the array and all synced well.

So, now – all of my 24/7 uptime drives are mirrored and I’ve got some research notes for how to move things around to larger drives when the time comes. I still should add a to-do item to check and see how many more sata drives I could squeeze into my desktop or server – it might be nice to have a hot spare.

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