12. Conclusions
A RAID 5 NAS can provide everyone in your home with a simple way to back up and move large amounts of data. My household's NAS is a critical piece of infrastructure to support the evolution of self-expression in schools. Where I wrote papers by hand for middle school and high school classes, my sons cut CDs, use desktop publishing, and create movies - using the NAS to move iMovie and iDVD projects from computer to computer. And, because the kids forget about the projects and leave them on the server, an archive of their creativity is automatically made. (I also secretly horde my kids' art projects in paper form!)
So should you buy or build a RAID 5 NAS? The better question is, "why should I put off moving my data to RAID 5?" As we acquire gigabytes (and in some cases Terabytes) of valuable content in digital form, the robustness of that data becomes an increasingly important issue. Anyone who has had his or her iTunes library wiped out due to a hard drive failure already has felt the sting of relying on a single drive for data storage.
Storage and / or backup on a RAID 5 NAS can provide a step up in keeping your data safe from hard drive failure, but can't protect against fire or theft or an angry teenager out to teach the folks a lesson. So it can be an important part of a data security plan, but not a complete substitute for a comprehensive backup strategy.
The make versus buy decision is likely to be shaped by the size of your pile of old equipment. Many people already own all the hardware needed except the hardware RAID card. Any old "too good to throw out, but not good enough to use" PC is a candidate for becoming a RAID 5 NAS. With an $80 MegaRAID card (and maybe a cheap gigabit NIC) you can turn "ol' dusty" into a very good RAID 5 NAS for a very low price.
interesting article, but the beauty of linux software RAID5 is that an array rebuild will happen automatically when you replace the faulty drive (well you have to tell it that you replaced the drive using mdadm). you can even simulate a failure and then watch it rebuild the array to get an idea of how your system will respond under different scenarios. here's a snippet of what needs to be done to replace the missing drive/partition:
Rebuilding:
To remove the failed partition and add the new parition:
mdadm /dev/mdX -r /dev/sdYZ -a /dev/sdYZ
where X is the array number (0,1,etc) and YZ is your disk/partition (sda3 for example)
e.g.:
mdadm /dev/md0 -r /dev/sde3 -a /dev/sdr3
(where sde3 is the 3rd partition on your faulty drive, and sdr3 is the 3rd partition on the new drive)
Watch the automatic reconstruction run with:
watch -n1 cat /proc/mdstat
I understand that people fear the console commands. It can be a bit scary at first. But mdadm is pretty simple when you're used to console apps and a little bit of linux. It's mostly just mdadm and such. I currently run two software raids with 7 and 5 disks.
i believe his concerns with software raid5 were not just the rebuilding points. i believe he liked the fact that if the os drive took a crap, he could take the card and array and move it to any operating computer and it would power up and work. if you lose the operating system that wrote the software raid array, you have lost the array.
Hi! I have now suffered RAID5 failure due to one failed disk and the status now of my RAID5 controller is degraded.. Is it safe to rebuild the same failed drive? we're using MegaRAID WEBIOS controller? will the data be lost if we do this?
We are in the hesitation mode of doing this..
I hope this will be stressed out...thanks for your help!
re: above
You will regret it.
Do not try to rebuild your raid array with a drive that already failed. I cannot say 100% b/c I do not use MegaRAID controllers, but it is telling you to get a new drive. Go get a new drive and follow the rebuild instructions for your controller. It is trying to save you.... don't outsmart yourself here