RAID - Hardware Needed?

autiger

I am moderately experienced in computer building and have a few questions about setting up a RAID array for data storage. I currently have about 400GB of media files (music, movies, photos) and am looking to add storage space for future expansion. I initially thought setting up a RAID 5 array with four 500GB hdds would be a good idea.

Question 1 - should I even try RAID 5 or just put the hdds in the computer and use them independently?

Question 2 - if I do pursue RAID, is RAID 5 the way to go? How should I set it up? Do I need hardware or should I run it off the on-MOBO controller?

I like the idea of keeping my OS and installed programs on a single drive and ALL of my media data files separate. I am currently running WIn Vista (Home) on a ASUS P5NSLI mobo with 3GB RAM. I think I can go buy 4 500GB SATA, 16MB cache drives for ~ $100 each... What are the implications (performance, security, etc) of running the OS on the non-RAID drives?

As far as backups go - I backup the stuff I CANNOT lose (photos, music, etc.) onto a removable drive that I keep in a fire proof safe. I would hate to lose the other stuff, but it would not kill me if I did.

My thought behind RAID 5 was to get a lot of extra space, good protection from data loss and performance increase.

Thanks for any advice.

Tex

A couple misconceptions with Raid-5.
1) Not sure at all what you meant by a LOT of extra space. As opposed to your other plan (just regular seperate drives... which I support btw...) you lose space.
2)The protection from data loss is solid. I have never used the raid-5 on MB's these days. But always with higher end hardware controllers. Works great especially with a hot spare online. Sweet
3) Ok lets get to the performance increase. Your performance is gonna go down. The writes are by nature bad. Its has to to read from the other drives in the array to get parity info before every write.

So every time you want to write to that four drive raid-5 array you gotta stop first and READ from those other drives. To get the parity info. (where to write the redundant data for the fault tolerance) Meaning your heads moved so not only did you do all those reads but now your also not writing sequentially really as the heads can't stay locked on the writes with the reads in between. There is a way to calculate that info with a 3 drive array on the fly..... But above 3 you read from all the other drives. So be careful with benchmarks. Look your talking about buying 4 - 500 gb drives? Is that enough for all your crap and room to back EVERYTHING up if at all possible. Thats a perfect world which maybe we can't reach but THAT should be the plan.

Once we get a firmer grasp on the total data space we need for you then we can calculate what we need for a backup plan.

Consider raid-1 and mirror one or two drives.

Cheers and Best of Luck

Tex

autiger

Tex,

Thanks for the reply.

I was under the impression that RAID generally provided BETTER performance than just standard drives. As I understand it you are now asking 4 drives to retrieve the same data that you would otherwise be asking 1 to get. 4 pipes > 1 pipe. I understand that RAID 5 has to read and write parity bits but thought the benefits still outweighed the negatives. Maybe this is just in a RAID 0 config?

As far as RAID 1 goes...I would hate to buy 2TB of space and only use 1TB... I understand it is the MOST fault tolerant but am not sure I want to sacrifice the space. I currently have ~400GB of files (of which ~70GB are stuff I would not want to lose thus I currently back it up on the external drive stored in the safe.) The other ~330GB is primarily movies and such - from ReplayTV, Tivo and other sources - that I don't want to lose but will not kill me if I do. I anticipate that this portion of the overall file size is going to grow rapidly - planning on getting a HD Tivo in a bit - and think that 2TB of space should last me for quite a while.

So based on this would you recommend plain old disks or RAID?

Thanks

mas0n

Unless you shell out the money for a RAID controller with an on-board XOR processor, RAID 5 will be VERY slow to write and get incredibly average read times. And by slow I mean ~15MB/s

In situations where both performance and redundancy are needed, I am a big fan of RAID 10 because even cheap RAID controllers support it, but again you sacrifice 1/2 of your potential storage space.

Tex

raid-0 stripes your data across multiple drives and is faster FOR SOME THINGS and slower for others. But reads and writes are faster if you spend enough time tweaking and tuning them to max the performance for your application.

But if you stripe 4 drives off your MB in raid-0 there is no redundancy. You have one drive much up and you lose it all.

Raid-1 gives the reads a boost if the controller handles it properly as it can read from both. The writes are the speed of a single drive. This is simple to implement and to recover from a drive failure.

raid-5 is much better IMO on higher end hardware raid cards with lots of cache and a onboard CPU to help speed things up.

If you want to do software raid-5 which is all the raid on these MB's is... Just know that the writes are going to be slow. They are also SLOW on high end raid cards.

Now if you were just using the raid-5 to sorta archive stuff off. You were mostly reading only and not doing a lot of writes then you might still be OK.

So what if we set you up where you buy 2 TB and get 1.5 TB?

use raid-1 to mirror two drives. This is where your most critical data goes. But you also have two more 500 gb drives. So you get 1.5 TB total. Same as with raid-5.

But consider this.... With the way prices on drives are dropping so fast and the drives are getting bigger and cheaper... Can you get by with TWO drives now? And then add more as the newer and even bigger drives drop. In 4 or 5 months you might welll be able to add a pair of 750's instead of a pair of 500's today that you don't need yet.

I know it sounded cool to grab 4 of those 500's for raid-5 tomorrow but.... If you won't need that extra storage hold off. Doesnt help you to have more drives in there right now generating more heat and slowly wearing out before they are even needed.

autiger

Tex - thanks for your help. I think the last point you made is right on - and it is probably based on this that I will make my decision. Prices for drives (as with almost everything else in technology-land) are coming down and I don't necessarily need the entire 2TB right now.

I think I am going to abandon RAID in favor of a bunch of disks.

I am going to stick with my current backup plan (external backup for "cannot lose" files) and take the risk of individual disks crashing and losing the other files.

Question - is there a limit to how many disks a Win Vista machine can handle? I believe my mobo supports 4 SATA plus a couple of IDE. Also, would I get the best performance from installing the OS on a new fast HDD? I currently have the OS on a 250GB ATA 133 HDD (just what I had when I built the computer). I have most of my media files on a 250GB SATA II(7,200rpm, 16MB buffer).

Any recommendations on a drive for the OS...or a large (500GB+) drive for the media files? I usually just look through reviews on newegg and then price shop around.

Finally - know of any good performance testing apps to rate my drives?

Thanks again for all of your help!

Tex

Vista does not have a limit taht I know of. You can fill that MB and then start adding in additional cards if you want. Think more about where the drives will be mounted and the heat they generate and the power they pull. I have not used them but they have external bays for sata now. Might be nice for sound and cooling to have those sata drives external.

A raptor is a fine OS drive. They are fast but really with a really fast big sata drive I doubt you would feel the differance. Go check out the ratings at storagereview.com. I used to post in their forums a lot.

Winbench is a great all round benchmark but ATTO tells ya a lot on transfer speeds. Try just using it and Sandra unless you get heavy into bench marks and your setup is not that tricked. Just use the benchs to make sure the drives are performing properly. With the raid arrays we used to spend DAYSs tweaking and tuning over and over trying to win benchmark wars... But thats all they were. Benchmarks.

Cheers

Cowboy