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Author Topic: Anyone familiar with RAID?  (Read 4606 times)

wraith808

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Anyone familiar with RAID?
« on: February 22, 2008, 12:43:13 PM »
I just received a new laptop... but I also just found out something troubling.  The laptop has 2 200GB Drives, which I just assumed they'd send to me as 2 drives.  But it's RAIDed ... RAID 0.  I have *never* used RAID 0 before because of the chance of all of your data going poof... but I just wanted to ask if I'm being a bit too paranoid...

I was thinking of buying an external and just keeping backups updated, but I'm terrible at that.  Is it a large chance that I'll be screwed?  And if a drive does die, is that pretty much it for the data?  How about if the controller dies?  I know that in the case of RAID 1 if the controller dies, you can just replace it and have no problems, but I know painfully little about RAID 0.

Thoughts?

tinjaw

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Re: Anyone familiar with RAID?
« Reply #1 on: February 22, 2008, 09:21:54 PM »
RAID 0 does what is called "striping". This means it writes part of a file to one drive and part of the file to another. This is done because it is faster to write  half of a file to two drives at the same time then all of the file to one. You can also read it twice as fast. RAID 0 is done for speed.

RAID 1 is where the whole file is written to one drive and an exact copy is written to the other drive at the same time. This is done for safety as one drive can died and the files are still available on the other drive.

Back to RAID 0 and you can see the problem, as if one drive dies you are only left with half of every file and no way to determine what the other half should look like.

HOWEVER, RAID 0 is no more risky than have one large drive with everything on it. In either case, if one drive dies, you lose everything.

I find that StorageReview.com site has the best textual description of RAID and AN&NC has the best animations explaining RAID.

Since laptop hard drives are (usually) slower speeds (to save battery power and run cooler), having a RAID 0 will speed things up. And then you should do regular backups to a large external HDD.
« Last Edit: February 23, 2008, 01:46:24 PM by tinjaw »

wraith808

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Re: Anyone familiar with RAID?
« Reply #2 on: February 22, 2008, 11:15:33 PM »
For the future, in case anyone else is dealing with this:
http://www.tomshardw...raid_scaling_charts/

That gives a *whole* lot of information about RAID performance gains.  Thanks for the information!  The part I was sort of skeptical about is the fact that RAID 0 is statistically a little more risky than having one drive.  Assuming that all of them have the same reliability, you have twice the chance of failure as if you use one drive.

But since I'm going to eventually upgrade to 2 7200RPM drives, I'll try RAID 0 for now- hopefully it will get me into the habit of backing up more often.

Thanks again- especially for the links!

f0dder

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Re: Anyone familiar with RAID?
« Reply #3 on: February 23, 2008, 12:49:53 PM »
Single drive dying in a raid-stripe (not strip :)) configuration = bye bye, data. Striping is done in blocks, rather than individual sectors, and a common block size is 64kb... this basically means that you lose every other 64kb of every one of your files. How bad that's going to impact you of course depends on the file formats, but generally - you're screwed.

Sounds like you bought one of those "performance PCs"? If you can live with only 200 gigs of storage, set up a mirror instead. If the RAID solution is worth anything, you get single-drive write speeds, but double the read speeds. Intel RAID Matrix stuff (introduced with their ICH8R chipset, I think?) is pretty nice, and even allows you to have both a mirror and a stripe part even though you only have two harddrives - ideal if you want both speed and safety, but for different partitions.
- carpe noctem

wraith808

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Re: Anyone familiar with RAID?
« Reply #4 on: February 23, 2008, 09:43:20 PM »
Yeah... it was the Sony VAIO AR-770 laptop.  I suppose I should have realized they were going to RAID the drives, but I didn't.  For now, I'm sticking with the RAID 0 and just doing regular backups... when I replace the HDs with 7200 RPM drives, I'll fix it then.