Does RAID make a real world difference?

[serialb]

I have 2 Quantum AS drives in RAID 0 config on a Promise FT66 card. I hardly see any performance gain in Windows loadup.

I have also tried a few benchmarking programs but none of them reports a transfer rate anywhere near twice as fast as single drive.

Anyone know of a benchmarking program for IDE RAID?

 

[irrigating]

<< Perhaps I'm too "casual," but I don't see how the operating system would be configured any differently - both configurations mentioned above are 120GB drives as far as the OS is concerned. >>



<< Care to explain this? For example, how would your filesystem setup for one 120GB drive be any different than for two 60GB's in RAID 0? >>



Theres two parts to this in RAID 0(stripe).

The second part first, your file system. The FAT (file allocation tables) can have cluster sizes of anything you want and the size of the cluster should be sized to your RAID requirement. You can do this a couple of ways, either as a new install in FDISK specifying the Z/switch or with a proggie like Partition Magic.
Be warned your partition sizes will be dictated.

Now for a faster start-up. The old default stripe size of 64 was fine for slower drives of up to 6 Mb/s when the fastrack and others were introduced. Todays faster drives will show little improvement at that setting. Try 32 and even 16 for the stripe size with todays drives. This is set in the controller BIOS. You will have to backup and reinstall if you're not doing a new install. Also be warned that the CPU usage will be inversely proportional to the stripe size. In other words a 64 stripe @ 3% CPU usage will become 6% usage with a 32stripe, 12% usage with a 16k stripe ect. You get to pick your performance.

Go to
http://storagereview.com/ for a better explanation.

This subject has been covered extensively in lots of other sites, search amdmb.com and ocworkbench.com. I'll see if I can did up the some links.

P.S. like to use 32k stripe for the RAID and 16k for the F.A.T. I tried all combinations a few years ago when I got the first Fastrack onto a BH6. Took all day for re-installs and such. Talk about no life,LOL😱

 

[cleverhandle]

<< The second part first, your file system. The FAT (file allocation tables) can have cluster sizes of anything you want and the size of the cluster should be sized to your RAID requirement. >>



OK, I've heard this much before - somebody quoted Paul's FAQ on this a while back. But I must say this makes *zero* sense to me. I understand the difference between the stripe and the cluster size. But I don't see how tweaking your cluster size here is any different than doing so for one disk. In either case, you generally improve performance at the expense of disk space by increasing the cluster size (more slack, but a smaller FAT). Why would your choice of cluster size be different on an array?

Please explain, in detail if possible. Or give more specific links - I've spent plenty of time reading SR, too, but I haven't seen this "stripe/cluster link" mentioned there.

 

[irrigating]

<< you generally improve performance at the expense of disk space by increasing the cluster size (more slack, but a smaller FAT). Why would your choice of cluster size be different on an array >>



No, actually you get increased performance by decreasing the cluster size. And you gain disk space. With large drives you may be forced to partition depending on how small the cluster size is set.

As far as why this all works has to do with allowing the RAID controller to work more efficiently, chewing on the optimal file size as it multiplexes across channels. Efficiency is the key word here, and settings will vary according to your intended application.

Tom P.

 

[cleverhandle]

<< No, actually you get increased performance by decreasing the cluster size. >>



My understanding is the opposite. Smaller clusters mean greater fragmentation and a larger FAT.



<< And you gain disk space. With large drives you may be forced to partition depending on how small the cluster size is set. >>



Yup. I agree there.



<< As far as why this all works has to do with allowing the RAID controller to work more efficiently, chewing on the optimal file size as it multiplexes across channels. Efficiency is the key word here, and settings will vary according to your intended application. >>



This is not really an explanation. Yes, the intended application affects cluster size, but why would that be any different on or off an array? I'm not saying that the default cluster is always the best, I'm just asking why the cluster size should be linked in any way to RAID striping.

 

[Quad]

the increase in performance with raid 0 is really obvious once you start using it. reading/writing it a lot faster. as someone mentioned before, copying files, loading programs happen quickly. the factor that i was most pleased about was the increase in network transfer speeds. with my 100mbit network, my top upload speed was 8000k, fluctuating up and down. after installing raid 0, my transfer speed was well above 9000k STABLE. as you can see, read speeds increase noticeably.