RAID 5 - A bargain or a stick of dynamite?

My three 1TB disks just came in the mail today, which has got me thinking about what I'm going to do with them.
The obvious choice for me was to short-stroke a RAID-0 for my OS and use the remainder for RAID-5 storage.

However, a little bit of searching over the web has turned up a great deal of information discouraging the use of RAID-5. The saving grace for RAID-5 is the fact that much of this information is ten years old, or more!...

... For those who have used RAID-5 on ICHxR chips, and are sound of judgment with these sorts of things, has RAID-5 matured in to a practical solution for a low-budget consumer?

My main concern is that, should a single drive fail, my PC will be totally crippled in performance until the drive gets replaced.

To give full perspective, my other consideration is to just order another TB and perform a "10" array for the entire volume and scrap RAIDing partitions.

For RAID5 I'd recommend a good RAID card ($300). The Intel controller is good for RAID0 or RAID1....not so good for RAID5 IMO.

People only seem to think about drive failures when they talk about RAID. There is a lot more that can go wrong and make your massive array unrecoverable w/o spending a small fortune.

In your situation I'd go w/ a 4 drive RAID0/RAID10 array...or an SSD + whatever you need for storage. The latter being the best choice for an overall better experience with less headaches.

RAID5 can give you a false sense of security. Businesses that use RAID5 only use it to preserve up-time, not backup their data...they use tape or similar to backup their data. A real backup solution w/ an external drive you can take off site is the only true way to keep your data safe.

SSD + 1TB drive for storage + 1TB external drive for backup = excellent PC experience w/o the headaches of RAID and data that is much safer.

Or do what I did and just run a single fast HDD (or SSD) in the main rig, and build a unRAID file-server for your data.

Jason hit most of the high points in his post. I'll try to add what I can and hope it's useful in your decision making.

What you have to consider is the amount of performance expected, how important data integrity is and how much you're willing to invest to achieve those goals.

Most data loss is going to occur from hard drive failure. That being said, you must also consider array corruption from flaky controllers, power surges and even faulty ram/CPUs writing invalid data. It doesn't matter how much redundancy is in place if the data being written isn't valid to begin with.

Ideally RAID 5 would be a solid solution. But as Jason pointed out, with the integrated controllers it doesn't perform as expected. Even when performing optimally, the potential for data loss is still slightly higher than a 10 array.

RAID 10 is a step above RAID 5, but with the added expense of another HD. Performance would surpass a single drive setup, but data security isn't a good as it could be.

A RAID 0 array would be a decent solution with a networked server as a backup. But then you get into the hassle of setting up a file server.

I would go one two different routes myself. If performance is a must have I would go with a SSD as the primary drive, Raid 0 two of the 1TB drives, invest in a good docking station and use the 1TB drive (or even sell it and pick up one of the cheaper lower performing 1.5TB drives) to use for imaging backups. That will give you solid performance across the board and allow you to make secure backups that can be stored away with minimal risk of data loss. That is also the most expensive solution.

RAID 0 on two of the 1TB drives with the third as a backup solution would also work. However it should be noted that 2TB of already heavily compressed material (video files, mp3s, etc) may not fit on the 1TB backup no matter how much compression or how good the backup software is.

Thanks for the advise. I appreciate it. I'm pretty well decided that RAID 5 would be a poor choice. Poor balance of cost versus safety/volatility.

I don't find myself very receptive to the idea of SSD. While the cost per gig has improved a great deal, it's still not at a point where I would consider it a very good investment. Having just my O/S on an SSD isn't good enough. I think what I like best about my current RAID 0 setup (Matrix RAIDed a 1TB with a 500 GB) is the improved load times in my games.
I feel like I couldn't get a large enough SSD to justify putting games on it.

On the other hand, using a pair of TBs in RAID 0 and the third in a backup configuration is a really good idea.

I didn't really understand your comment on "2TB ... material ... 1TB backup no matter...". If I RAID 0 two 1TB volumes, I'll have - at most - 1 TB of data to back up.

more thoughts:

Should I RAID-0 two volumes and use the third for backup, is there any way I could have the third volume imaged in such a way that I could include it in the RAID-0 with one of the other drives in the event of a disk failure? Or would I have to replace the RAID disk and reimage it?

If you RAID0 two 1TB drives you'll have a 2TB array. RAID0 offers no fault tolerance and gives you twice the speed.

So, if you have a 2TB array using 2 drives and that array is near full you probably won't be able to backup that array to just a 1TB drive. You can use compression, but I doubt it'll be enough. Still, you probably won't have to worry about that for a while.

Now you could do a RAID1 array w/ 2 1TB drives, and then you would only have a 1TB array, but you'd have no speed benefit.

You can't use a hot-swappable drive for RAID0. If the array fails it's pretty much gone. If you've done a backup, though, all you have to do is restore it.

1 possible idea is to do a Matrix RAID split w/ 2 drives. Create the first array as a RAID0 and make it ~200GB (or whatever you think you'll need). Then create a RAID1 array w/ the remainder...in this case it'll be around 900GB. Then you should be able to backup everything to the external 1TB drive even if you're maxed out using a little bit of compression. And you have a little extra security knowing that you now have 3 copies of you're data.

>> If you RAID0 two 1TB drives you'll have a 2TB array. RAID0 offers no fault tolerance and gives you twice the speed.

Yeah, I realize this. I have no idea what I was thinking when I wrote that. I must've been still thinking about RAID10.

The RAID-1 + backup isn't a bad idea, but I think I'll stick to RAID 0 + a selective backup. Thanks for the tips.

You do know you can do both at the same time w/ Matrix RAID, right?

That's what I was proposing. Slice out 100GB from each drive into a 200GB RAID0 array, and take the remaining 900GB from each drive and RAID1 it for redundancy.

Doing it all RAID0 has the benefit of making everything faster, though.

Logical Partition raid is a bad idea though. Just keep your drives in logical arrays and get another set if you really need raid 0. I never did see good performance using raid partitions.

I have had very good luck with Raid 10 setups. As Jason has mentioned a Raid0 slice for the OS + Raid 10 for data is a great way to go. Currently I am running a single SSD for my boot drive and a couple of 1TB drives on mirror for all my dada. Then I have a 4TB NAS drive on my network for stashing extra files and backups.

visbits said:

Logical Partition raid is a bad idea though. Just keep your drives in logical arrays and get another set if you really need raid 0. I never did see good performance using raid partitions.

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Not sure what you are talking about here. I have seen very very good results using this method. Any more though, I think its nuts to spend alot of money on multiple drives for Raid 0, vs , bite the bullet for a $130 SSD that will smoke any number of raided mechanicle drives.

Kivin said:

>> If you RAID 0 two 1TB drives you'll have a 2TB array. RAID 0 offers no fault tolerance and gives you twice the speed.

Yeah, I realize this. I have no idea what I was thinking when I wrote that. I must've been still thinking about RAID 10.

The RAID-1 + backup isn't a bad idea, but I think I'll stick to RAID 0 + a selective backup. Thanks for the tips.

Click to expand...

Even with a RAID 10 you would have a 2TB partition. Basically you would think of the 10 array with two drives in RAID 0 and two drives in RAID 1 mirroring everything the first two drives did.

RAID 1 will show some improvements in read performance, but takes a small hit in write performance.

For what you've described you want, I would suggest you reconsider an SSD as a possibility. With 2 TB of storage (which is what you seem to need) I would think most of that is media content. If that's the case it shouldn't matter if it's in a RAID array or not. For that matter, it could be on a 5400RPM drive and you probably wouldn't notice. I recently bit the bullet on the 120GB Agility drive on newegg for $320 with $30 MIR. After a full windows 7 x64 install and AV software I'm at ~20GB used space. I figure after Photoshop, Dreamweaver, Office, etc I should have 60-80GB for game installs. I don't know how much you keep installed, but that should be plenty for most people. Anyway, I know the $/GB isn't where a lot of people would want it and I couldn't fault anyone who would want to wait till the new year and see where prices trickle down to. If it's great performance you're after though, that's your best bet.

With just the equipment you have now, RAID 0 with the third drive as a backup seems a prudent choice. I would suggest picking up a docking station though. Decent eSATA/USB 2.0 docks can be had in the $30 range. It may be just me, but it's reassuring to know that my backups are sitting packed away and not exposed to possible power surges or other component failures that could leave them useless.

hyperasus said:

Not sure what you are talking about here. I have seen very very good results using this method. Any more though, I think its nuts to spend alot of money on multiple drives for Raid 0, vs , bite the bullet for a $130 SSD that will smoke any number of raided mechanicle drives.

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$130 is not going to buy much of an SSD you can either go larger sacrificing performance to standard drive levels, but with more complications, or get one that performs well and can basically handle an OS install a couple of gmaes and all storage will have to be on mechanical drives.


Or $130 can pick up a couple of decent performance mechanical drives that you can raid together for performance or data security.



Personally I am holding off on SSD until I can get 200MB/s performance on at LEAST a 100GB drive for $100. It should not be much much longer

Let me just confirm... must I have an even number of disks to perform a RAID 0 or RAID 1 (not RAID 10).

I'm either going to RAID 0 the two volumes and use the third as an external backup, or short-stroke the three volumes and use the remainder for redundancy.

Kivin said:

Let me just confirm... must I have an even number of disks to perform a RAID 0 or RAID 1 (not RAID 10).

I'm either going to RAID 0 the two volumes and use the third as an external backup, or short-stroke the three volumes and use the remainder for redundancy.

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I think it'll help if you translate RAID 0 = striping and RAID 1 = mirroring in your head as you read. RAID 10 is striping with mirroring.

For RAID 0 you can have 2 or more drives. Not sure if there's a drive limit, I suppose it would just be the limits of the controller.

For RAID 1 you must have an even number of drives as everything written to the array is written to two disks.

RAID 10 is bound by the limits of RAID 1 and must have an even number of disks as well.

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

Short stroking is really only useful, IMNSHO, if the remainder of the drive is left unused. The second you start sending the read/write head outside of the boundary set by the partition when short stroking you've lost any performance benefit.

I think you may be on information overload here. It happens to me a lot on these forums with so many knowledgeable members here. With your current hardware RAID 0 with the third drive as an external backup is a sensible choice in terms of performance and data preservation.

jason4207 said:

RAID5 can give you a false sense of security. Businesses that use RAID5 only use it to preserve up-time, not backup their data...they use tape or similar to backup their data. A real backup solution w/ an external drive you can take off site is the only true way to keep your data safe.

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I think this is a good point - a proper backup strategy is incredibly important. We use a RAID 5 for an important machine in the office, but we still have a plan in place for regular backups to DVD. The RAID 5 just means that if a hard disk dies, we don't lose the job its running (it runs jobs that can take up to 3 weeks).

"The RAID 5 just means that if a hard disk dies, we don't lose the job its running (it runs jobs that can take up to 3 weeks)." that really sums up RAID 5 rather well. Thanks.

@TheGame240: I believe I fully understand the difference between RAID 0, 1, 10. It still seems to make sense in my head that a RAID controller would support an uneven number of disks > 2 in a mirroring operation; but I understand that is not the case.
What I was looking for is Drive 1 == 2 == 3. I guess RAID 5 does make sense for some people. Though, without an external backup, it really isn't a good choice for me. It'd be more cost efficient to administer myself a RAID 10 than a RAID 5 with backup.

I just ran across this and found myself wondering why nobody suggested short-stroking the first two 1TB drives by 50% and striping them into a total ~1TB array, then dedicate the third drive for backup/redundancy. That was the first thing that popped into my head.

I just may try that myself.