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Balanced view on RAID 5?

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August 2, 2008 5:15:09 PM

For some reason people seem very opinionated about raid 5 and I'm trying to figure out why (largely negative). I know the write speed is going to be slower on raid 5, but I want to build a hassle-free system that I don't have to backup. I'm trying to limit my budget on a PC to about $11xx and really thinking of 3 500GB drives. I've read that the read speed is good, but is the write speed really as horrible as people make it out to be? In one thread I read that if the data file is larger than a single stripe it writes quickly because it doesn't have to do any calculations, in others I've just read it's slow all around.

I'm pretty much just asking if using 3 drives in raid 5 is suitable for torrents/gaming/school work. I don't do any video/photo editing or graphics stuff. Also suggestions on stripe size? I've never set up a raid before.

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a b G Storage
August 2, 2008 6:19:51 PM

Any particular reason to go for raid 5 rather than raid 1? True you get less capacity with raid 1, but large capacity disks are pretty cheap nowadays.

If you particularly want to go with raid 5, it doesn't sound as if write performance (which will suffer for small files in raid 5) is particularly critical in your applications. People are normally worried about databases when criticizing raid 5, but torrents/gaming/school work aren't going to make heavy demands on the I/O subsystem.

But - and a big but - no raid level is a substitue for regular backups. You may find doing this a hassle but when the power fails, when the virus strikes, when you delete the wrong directory (when the dog bites, when the bee stings, etc.), you'll find it far more of a hassle. Raid won't protect you against those mishaps, just against a disk failure. It doesn't have to be difficult to do backups; get an external hard drive and any one of a number of programs (some freely available on magazine cover CDs) that will automatically back up your system. You may never need these backups, but if you do then you'll really need them!
August 2, 2008 6:27:06 PM

No. Any kind of RAID requires more regular backing up than a single drive system. RAID introduces driver issues, not to mention that if you hose your OS and have to transfer files from your disks to another PC you cannot do that. RAID is not a form of backup, and RAID is far from hassle free.
In terms of speed alone RAID 5 will be slow if you run it on an onboard controller. The only performance gains to be had are found in RAID 0, and in expensive enterprise class multidisk arrays.
I'm not saying that RAID is bad, its just not a backup. RAID is great for servers and workstations that have niche needs.

As for my personal view on the subject, RAID 5 has no business in a desktop PC. With the money you have in your budget you would do well to buy an external backup device and make regular backups of anything you want to keep, or just get 2 internal HDDs and look for some automatic backup software like this

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

This device would be another cool idea,
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
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August 2, 2008 6:32:35 PM

happy_fanboy said:
No. Any kind of RAID requires more regular backing up than a single drive system. RAID introduces driver issues, not to mention that if you hose your OS and have to transfer files from your disks to another PC you cannot do that. RAID is not a form of backup, and RAID is far from hassle free.
In terms of speed alone RAID 5 will be slow if you run it on an onboard controller. The only performance gains to be had are found in RAID 0, and in expensive enterprise class multidisk arrays.
I'm not saying that RAID is bad, its just not a backup. RAID is great for servers and workstations that have niche needs.

As for my personal view on the subject, RAID 5 has no business in a desktop PC. With the money you have in your budget you would do well to buy an external backup device and make regular backups of anything you want to keep, or just get 2 internal HDDs and look for some automatic backup software like this

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

This device would be another cool idea,
http://www.newegg.com/Product/Product.aspx?Item=N82E168...



Concur.
RAID 5 REQUIRES BACKUPS!!!!

It does not protect against Virus, File Corruption, Accidental Deletions, Raid Card Failure (It could be tough to get a matching RAID controller and then you lose all data), and more.

YOU MUST BACKUP.

As stated above, a simple backup method is to automate Backups from One Device to Another.
Lots of software can do that.
August 2, 2008 6:45:28 PM

I agree with the comments above but if you do decide to RAID your drives the controller makes a huge difference. A dedicated card is the best option but if you use your motherboards controller keep in mind that Intel's Matrix Storage is significantly faster with less CPU overhead than Nvidia motherboards.
August 3, 2008 2:39:08 AM

Ah... I kinda didn't explain the situation too well. What i meant by backups is that I'm only worried about HD failure rather than viruses. The only reason I considered raid 5 over 2 raid 0 and a backup was because raid 5 can preserve all my data if a single drive fails. But now that I think about it I guess I'll just go raid 0 + auto backup and save some of my files. Goodbye anime T_T

Thanks for the input
August 7, 2008 10:10:28 PM

I see a lot recommendations of RAID 1 rather than RAID 5.

That works only in the smallest RAID systems. In a large RAID system, the economies of scale in RAID 5 far outstrips RAID 1 or RAID 0+1/1+0.

For e.g. (in this following illustration I say "raid 1" as a short hand for "raid 1+0" or "raid 0+1" variants, doesn't really matter for this example's purpose):

6 drives; 1 TB each. Using RAID 1. I get 3 TB.

Same 6 drives, using RAID 5 I get (approx) 5TBs.

Go to 8 drives: RAID 1 -> 4TB; RAID 5 -> 7TB.

I used 1TB as illustration, you can use 500GB to do the math and RAID 5 still shows the economies of scale quickly.

You can't achieve the same capacity with RAID 1 variants and still be within budget!

In the 8 drive example, if my target is 7TB of storage, I need 14 drives to achieve that! 7 drives more than RAID 5! Now you've also added 7 additional points of failure, 7 additional components of complexity, ** AND 7 ADDITIONAL HDD TO HAVE BUS CONTENTION over the controller (which could potentially end up slower than 8-drive RAID5!) ** Plus, good luck buying a RAID controller with 14 ports vs a raid 5 controller with 8 ports (a lot more common).

Additionally, if I'm going to spend all the money that RAID 1 solutions needed (to go to 7TB) anyway; there are TONs of ways to increase reliability of my basic 8-disk RAID and still cost less than 14 drive RAID 1 variants:

- buy 2 RAID controllers! Guard against controller failure.
- Install an online hot spare.
- install a UPS
- Even going to RAID 6 would cost less than RAID 1/14 drive!

So unless you're talking about small scale RAIDs (3 or 4 drives), you can't implement the same things RAID 5's can do with RAID 1 variants, without cost (or sometimes even performance) going out of whack.

Now... if your argument is that why would a home PC need 8 drives RAID. Think about expansion. When you first buy the home PC, perhaps 4 drive RAID is ok, when you need space 2/3 years later? It's not hard to see things doubling to 8 disks.
!