RAID Array question ........ Help me I'm a dummy...... So many HDDs so little time..

[jpe20]

Hi folks.....

I am building a new PC system for the 1st time and I am thinking of buying a couple of hard drives to put in a RAID configuration for performance reasons.

My plan is to use a parity RAID config. so that I can use many inexpensive disks (ie Maxtors x 4stripe +1parity) in a RAID 5 or RAID 0+1 config. I have read the Wikipedia article on RAID and I am none the wiser (I am a fool!!!). So what do I need to buy hard drive wise to have the benefits of the performance increase from striping but the reliabilty of parity from an extra single drive. I don't understand the difference between RAID 5 and RAID 0+1. Ideally I would like to buy 5 cheap 250-300GB drives (Maxtor DiMax10 SATAII) use 4 for striping and 1 for parity.... is this possible under a RAID config??? and can I rebuild a drive if one of the 5 go faulty?????

Sorry for rambling as I am a little tipsy !!!!!!..... Just on my mind thats all...

System being built ASUS M2NSLIMB ... 2x7900GTX.... 3800x2 AMD oc ..... etc....

Just that I think the HDD performance is a major bottleneck in general windows performance so I am hoping that 5 drives in some sort of RAID config will mean that I will have a superfast system. [subnote ... just that seems cheaper than paying out for the WD Raptors with 10K rpm speed rating.... I am not rich!!!!]

Hope u guys can help....
Jules

 

[BillytheImpaler]

I don't know much about RAID arrays but I can help keep you on the good side of the mod team.

The rule for sigs is that a text-only sig like yours can contain at most 4 lines of text.

 

[smids]

Hmm, onboard RAID5 is usually poor - you need something to calculate the parity data which will be your CPU in this case meaning writes will be very slow (15-20MB/s) whereas reads should be normal (5 disks umm, maybe 175MB/s?). RAID0+1 is faster in this regard as it will write about the speed of a normal disk but read at RAID0 speeds (50MB/s write, 100MB/s read).

When you use a 3rd party RAID card, this may have a chip dedicated to calculating parity data (XOR calculations I think they are called - don't quote me) and this greatly improves writes. Factor in how important writes are - for installing, creating new files etc - will there be much of this or will it be reading data e.g. game maps, windows etc.

I'd say go RAI0+1 or just buy a 74GB raptor and a nice seagate 7200.10 - either way, get a Seagate 7200.10 as these are the fastest drives around for 7200rpm due to the perpendicular tech.

Hope this helps somwhat. Ask more questions if you need to.

 

[PobodY]

I don't know if it will really help you.
The major benefit of RAID is in simultaneous reads (or writes) - like when you have multiple users on a server because then you can read the one volume multiple times at the speed of one (if each user is using data on different physical disks).
A 100% redundant array (RAID0?) is also probably not worth your while - great for recovering your files if one drive goes down, but really it equates to half the space (i.e. 2x40Gb gives 1x40Gb RAID0 drive).
RAID1(?) is nice for the sake of spanning volumes, but is a giant pain in the ass if you loose a disk.
RAID5 can be expensive non? You need a proper RAID card to do that, not just the onboard chip or software... which probably means having 4 or five identical drives to make your array? Most likely SCSI drives to get a RAID controller like that?

Appologies if I've got my RAID formats mixed up, but I hope you can understand what I'm trying to say.

 

[BillytheImpaler]

A 100% redundant array (RAID0?)

That'd be RAID 1. RAID 0 is full striping. If one disk dies the array is destroyed.

 

[PobodY]

Thankyou. For some reason I always get those round the wrong way.
I think the point I was making is still valid though.
I'm wrong about the SCSI for RAID5 though - they now come in SATA as well, but I don't think you'll see a PATA one.

This is what Tom's Hardware says... look at the last paragraph.

 

[Beansprout]

RAID 0+1 is far better than RAID5 for most things. Google some benchmarks

 

[jpe20]

Thanks for your comments ........

Just to throw a spanner in the works I have seen some Western Digital HDs 250GB (won't say where forum rules) SATA II drives RAID edition. These seem meant for the server/enterprise market. Here's the crunch though .... They quote a MTBF (Mean Time Between Failure) of 1MILLION HRS thats 117yrs. I thought average consumer drives had a MTBF of 5yrs. (Theres a 5yr warranty)

If I believe the 100 odd year MTBF then even if I buy 4drives for 240quid(price around 70quid) then I still have an array of a combined MTBF of 25yrs or so ... still more reliable than a single SATA drive.

I am very tempted to go for 4 of these server HDDs by WD and put then in a RAID 0 config.

Can you partition a RAID array???? Just that I have a spare 300GB IDE drive that I would like to use as a backup drive. So I would partion my RAID array (RA) into a 300GB one (for OS and important work files ... to backup to IDE drive) and a 700GB (less important files like games and video files etc not critical for backup)... The RA will be 1000GB (4x250GB RAID edition WD SATA drives.).

What do you guys think?? If this is true what I am saying then I think overclockers should start selling some of these Western Digital RAID edition drives. Even though they are aimed at the server market they look or seem ideal for RAIDING up 4 drives together which would still be more reliable than a single domestic drive. To me it is impractical to run 4 cheap domestic drives in a RAID 0 config. As the combined MTBF would be just over a year(unacceptable).

By the way my mobo. is a ASUS-M2NSLi which contains NForce590 chipset and the manual says the onboard RAID controller will run RAID5 and RAID0+1.

My original idea was to get 2x74GB Raptors in RAID0 supported by a 300GB IDE Maxtor(already own) for backup of the RAPTORS. I would put my OS and speed crictical applications/data on these raptors. Then I would have 2 new (perp. rec.) 320GB Seagate 7200.10 in RAID0 config. to store less critical data like music files and recorded TV programs.

Just tp finalise I assume you could stripe 4 drives in RAID0 and get 4x performance (4x50-70MB/s gives 200-280MB/s more or less filling the SATAII bandwidth???

Wow thats a lot to nibble on there!!!!!

Sorry for the long post.....

Jules

 

[Dutch Guy]

Just tp finalise I assume you could stripe 4 drives in RAID0 and get 4x performance (4x50-70MB/s gives 200-280MB/s more or less filling the SATAII bandwidth???

In theory yes, in practice not really.

It will be faster with pure performance but things like game level load times will hardly change and the CPU usage will be higher with a RAID array.