HOWTO: 0.5TB RAID on a Budget

Compu486 writes "Inventgeek.com has a new how-to article titled 'The Poor Mans Raid Array.' The article details how to make a modular .5 terabyte Raid 5 array for under $250 (USD), and it all runs on the Mandriva flavor of Linux." Drive prices being what they are, this seems cooler than it is practical. Update: 06/25 23:31 GMT by T : If that's not enough storage, Yeechang Lee writes "Let me show off the 2.8TB Linux-powered RAID 5 array I built for home use a few months ago. I provide lots of details on how I did it, what I used, and the results. The Usenet thread has good followup posts from others, too."

Comments

typical?

[mnemonic_]

this seems cooler than it is practical.
Perfect for slashdot!

Re:typical?

[Rei]

Many home RAID setups that I have seen are more for show than they are as a speedup. Most of them are RAID 0 - i.e., they're for "performance", not redundancy (I assume the reason is that most people don't want half their space to dissapear with RAID 1, but don't want to have to use enough drives to make RAID 5 effective). Yet the primary performance limits on a home PC's disk performance (apart from operating-system issues like the filesystem and caching) are latency-based, not throughput based; RAID, if anything, will increase your latency.

If you want a high performance system, spend the money to get a small, top-of-the-line drive for your root partition (15k rpm SCSIs are nice, if you have a scsi card - you can get a 9 gig for 30$ including shipping, an 18 gig for 55$), and then put all of your space-consuming files (movies, music, etc) on your cheap bulk storage. Get enough spare ram to have good disk caching. And, of course, choose a good filesystem for small files - ReiserFS works well for me, but there are a lot of good options.

You only need major throughput if you're doing a lot of very long file reads that need to occur at top speed (i.e., not playing video or listening to music; more like what you need for running a large relational database, or being a fileserver on a crazy-fast network). To the "Raid 0" crowd: Does this really fit your disk's typical usage patterns?

Howto

[zabagel]

Possible new Slashdot Category?

Not a big deal.

[Seumas]

Okay, half a terabyte? Hardly worth lifting a finger for. I have more than 2.5 terabytes almost entirely of porn. And not only that, but it's all stored on 20 IDE drives of various sizes, in external USB cases, plugged into three 7-port D-Link USB hubs, plugged into a PC.

That's a lot of storage.

That's balls-to-the-wall.

I'll take a picture of all the drives stacked up on one another on the desk (5 rows, 4 drives tall).

I take my porn seriously.

Re:Not a big deal.

[Seumas]

Who marked this "Funny"?

I'm serious. And it shoudl be "Informative", you insensitive clods!

Re:Not a big deal.

[MustardMan]

I'll take a picture of all the drives stacked up on one another on the desk (5 rows, 4 drives tall).

With that much porn, I think the last picture /. geeks want to see is of the drives

Re:Now *thats* redundant.

[James Cape]

Actually, for RAID 5 you'd need a minimum of 3 drives.

http://www.acnc.com/04_01_05.html
http://en.wikipedia.org/wiki/Redundant_array_of_in dependent_disks

Re:Now *thats* redundant.

[Anonymous Coward]

You are really better off just using software raid as provided by the operating system than using the fake raid provided by those on board ide/sata raid controllers. Then if your mobo dies you don't have to find one with the same raid chipset, worry about proprietary drivers etc. You just get another mobo and everything works fine. I played around with the nvraid, the silicon image raid, and one other brand, and they all pretty much suck. The best part is that without a special driver it doesn't matter how you configure the devices in the raid bios, they show up to the OS as individual drives not as a raid drive.

My shorter HOWTO:

[Saeger]

HOWTO make a 500MB software RAID5 array for about $250:

1. Buy 3 250GB EIDE or SATA HD's very cheaply.
2. Plug them into your cheap linux PC (with at least a 400Watt powersupply). If EIDE then make sure each drive is on its own (master) channel. If your BIOS supports "hardware" RAID, disable it.
3. Use a low-level drive diagnostic fitness test to burn the drives in so you can be sure they won't fail right away. A great tool for this is The Ultimate Boot CD, as well as the 'badblocks' linux util.
4. Assuming your 3 new drives are drives sdb, sdc, and sdd, with your bootdrive on sda (or hda), you should now partition each of them (instead of raiding the entire disk). I recommend creating one primary partition which is slightly smaller than the fullsize of the harddisk, such that if you buy a replacement drive of another brand and it isn't the EXACT same size, you won't be SOL when adding it. Mark the partition type as "FD", which is the raid autodetect type.
5. Verify that your kernel supports software RAID by checking that /proc/mdstat exists, or by checking for the multidisk "md" module in the output of "lsmod | grep md" after attempting to "modprobe md" and "modprobe raid5". If not supported, then... figure that out yourself.
6. Now the fun part (assuming mdadm's installed):
   mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb1 /dev/sdc1 /dev/sdd1
   View the status of the raidset construction by cat'ing /proc/mdstat
7. Put a filesystem on the md0 device with mke2fs /dev/md0 (or mkreiserfs, or whatever)
8. Add a line to your /etc/fstab to automount your new raid array at /raid5 or wherever.
9. Oh, and if your distro doesn't automatically detect your array on reboot, you need to fix that by putting this in your init scripts somewhere:
   mdadm --assemble --scan

Now, wasn't that easy? :)

Re:Now *thats* redundant.

[Slack3r78]

That's exactly my experience. My family owns a PC shop, and we stopped buying WD drives around the time of their 30-60GBs because we were getting way too many failures - many DOAs and, worse still, drives that were failing a few weeks after being sold.

We've been selling pretty much exclusively Samsung and Seagate since then. The other *huge* often unmentioned advantage is that they're both much quieter than WD and Maxtor equivalents - Samsung being a little quieter in my experience.

Really, outside of the Raptor line, I see no compelling reason to buy a WD drive. I can definitely agree with the sentiment that I have *never* heard anyone say they hated Seagate drives, especially if you talk to the SCSI freaks out there. :-)

Re:Cool? Naah, old

[ZorinLynx]

Uhh, it'd be worse. You're more likely to have a double drive failure out of ten drives than three.

And a double failure is all it takes to take out a RAID5.

-Z

Logical Volume Manager

[mpeg4codec]

I'm surprised that nobody has mentioned the Linux Logical Volume Manager subsystem. It has many of the features of RAID arrays [such as spanning across multiple drives] with the added flexibility of being able to dynamically add [and theoretically remove] drives.

Unfortunately, aside from RAID'ing the volumes or something similar, I haven't been able to find any information on making the system redundant.

Read about it more on TLDP. It's a very robust system that works well on both servers and desktops.