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Raid1 or Raid5

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JCROCCO

Senior member
Mar 14, 2003
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I like the idea of raid5. It seems to offer redundency while using all available disk space.

Raid1 only uses space of 1 drive, and if corrupt data causes drive failure, both would fail.

Any thoughts, pros, cons?
 
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Rapidskies

Golden Member
May 27, 2003
1,165
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For a server always go Raid 5 over raid 1. As for your arguments Raid 5 actually loses 1/3 of the drive space (for 3 drive raid) and in your example if corrupt data causes drive failure your RAid 5 drive is toast as well. For your home system I wouldn't bother with raid but would blast an OS image every once in awhile to a spare disk & burn your data to DVD.
 
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MixMasterTang

Diamond Member
Jul 23, 2001
3,167
176
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Also depends on what the server is going to be used for. Raid 5 actually has a slower Write than Raid 1 because it has to Write the stripe as well. Raid 5 is definately faster on Reads though. You could go Raid 10 though for good performance and redundency.
 
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nweaver

Diamond Member
Jan 21, 2001
6,813
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I've never seen data corruption cause a drive to fail..it may cause the OS to fail, you may loose data, but not hardware failure of the drive.


Raid 1 is good for uptime (i.e one drive fails, you fail over to the other drive and don't have downtime)
Raid 5 is good for fault tolerance with more disks and striping (some performance increase). If you get nicer hardware, you can hotswap drives and rebuild the array without folks even realizing it.

Raid1 and raid5 have a place in a DRP. Raid1 and Raid5 are NOT a backup!!
 
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nweaver

Diamond Member
Jan 21, 2001
6,813
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The article did an OK job explaining the levels, but I wasn't too keen on some stuff.

The "raid controller" on most modern motherboards is more like "winraid" and isn't that great of a solution. In fact, I would gander a guess that switching from that to linux software raid with the same controllers/disks would yeild BETTER results. They mention raid for windows, but not linux. That's like talking about performance cars, mentioning a mazda miata and leaving out a corvette (yes, linux S/W raid is that much better then windows software raid).

good for raid level/parity/how it works type thing, not much else that was decent imho
 
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Madwand1

Diamond Member
Jan 23, 2006
3,309
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Um, sorry.. I came across an article recently that compared the performance of various RAID setups of one set of devices, and mis-remembered the source. In particular, it compared RAID 10 favorably vs. RAID 5. Anyone remember this one?

I think Bjorn is still relevant to the OP and perhaps others, but would like to also mention the Wiki article in a similar spirit -- it might be easier to skim as well.

http://en.wikipedia.org/wiki/Redundant_array_of_independent_disks

As to performance, big topic. I don't think I'd be satisfied by any single write-up as there are far far too many variables; I'd prefer to do my own benchmarks on my own relevant problems. Perhaps that's why I didn't bookmark the article I was thinking of. I look forward to whatever Storage Review comes up with though.
 
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MrControversial

Senior member
Jan 25, 2005
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Any sort of disk redundancy scheme should be Plan B. Plan A should always be some sort of disk-based backup. For home, I'd stick with a RAID1 scheme with a tape backup. For a medium sized business, I'd go with RAID5 and a tape backup.

For larger hard drives where tape isn't practical, I'd suggest a SAN or NAS solution.
 
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nweaver

Diamond Member
Jan 21, 2001
6,813
1
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Originally posted by: MrControversial
Any sort of disk redundancy scheme should be Plan B. Plan A should always be some sort of disk-based backup. For home, I'd stick with a RAID1 scheme with a tape backup. For a medium sized business, I'd go with RAID5 and a tape backup.

For larger hard drives where tape isn't practical, I'd suggest a SAN or NAS solution.
Click to expand...

With the advent of 600 gig tapes (compressed) I think tape will always be there. It's just to easy to have exec admins swap tapes and give the old to a courior for offsite storage. My wife used to do that for Well Fargo's insurance branch
 
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Madwand1

Diamond Member
Jan 23, 2006
3,309
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Originally posted by: MrControversial
For home, I'd stick with a RAID1 scheme with a tape backup.
Click to expand...

Can you suggest some affordable large capacity tape drives for home use?

Personally, I have a minimum of 200 GB of important data that I'd want persisted, and think offhand that a separate IDE drive, or even multiples of them could provide the best performance / price.
 
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Rapidskies

Golden Member
May 27, 2003
1,165
0
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Please don't get a tape drive for home use they break way to often and cost way to much. Get a usb or ide drive and some imaging software.
 
RebateMonger

RebateMonger

Elite Member
Dec 24, 2005
11,586
0
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The choice between RAID 1 and RAID 5 depends on your priorities. There are a couple of reasons why you might choose one or the other.

Among the two, RAID 1 has the lowest probability of data loss due to drive failure. RAID 5 is a BIT more likely to have two drives fail at once (and cause data loss) than a RAID 1 array.

RAID 5 is more space-efficient than RAID 1. If you want parity checking, but want to maximize your storage efficiency, then RAID 5 drives can do that.

RAID 1 is VERY convenient if you want to grab a quick image of your system. You can just pull one of the two drives and you have a instant backup. This can be handy if you are installing software that might corrupt your system (such as a Service Pack) and want to have a before/after copy. If you don't like the results of the Service Pack, just plop in the old drive and the changes are instantly gone. You can't do this trick with RAID 5.
 
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JCROCCO

Senior member
Mar 14, 2003
596
0
76
Good point.

Just FTR, I use a tape drive at the office. I just want data redundency.
 
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nweaver

Diamond Member
Jan 21, 2001
6,813
1
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Originally posted by: Rapidskies
Please don't get a tape drive for home use they break way to often and cost way to much. Get a usb or ide drive and some imaging software.
Click to expand...

my Onstream ADR (30/60 gig capacity) has been working great for a couple of years, and you can get them pretty cheap on E-Bay. I'll bet you can even get a DLT80 fairly cheap (haven't looked in a while). Do you have anything to show that MTBF on consumer level tape drives is more/less then hard drives?
 
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EatSpam

Diamond Member
May 1, 2005
6,423
0
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First, RAID is not a subsititute for a backup. If the computer writes corrupted data, the data is corrupted. RAID won't save you.

Second, go RAID 1 if you only want to have two drives and mirror them. Go RAID 5 if you have 3+ drives and want redundancy.

I use RAID 5 for my bulk storage and RAID 1 for boot devices/small servers. I will be going with a 4x74gb Raptor RAID 5 on an Areca controller in my Xen server I'll be building... since the Arecas are just so damned fast. :)
 
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FreshPrince

Diamond Member
Dec 6, 2001
8,361
1
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most server configs have multiple backplanes...

raid 1 for OS
raid 5 for data

some even go a little further and do

raid 1 for os
raid 1 for swap
raid 5 for da

for max performance.

I have heard horror stories fo raid 10 so I have never used it...besides, it's an aweful waste of disk.

raid 5 with parity and hot spare is really good, but for maximum protection you should go with raid 6, 2 parities and 2 hot spares.

hope this helps.
 
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