deciding what drives for a raid setup..

Col_Kiwi

Distinguished
Aug 8, 2002
429
0
18,780
Recently I got an Asus P4P800 mobo (onboard sata raid from springdale ICH5R), and I've been thinking my next upgrade should be drives for a raid array.

I was thinking about a rather pricey but awesome setup -- dual WDC raptors in raid 0. A friend has this setup and its very fast.

However, tonight something else occurred to me. I currently have and use a single WD800JB. With the immense price of raptors, for about $50 (canadian $) less, I could buy two more WD800JBs <b>and</b> a Promise PCI IDE RAID card.

What I'm wondering is, what would perform better?

The $50 is an issue for me.. but I could afford the raptors just by waiting a little longer. However, if the 3xJB setup can match the raptors in performance, I might as well do that considering it costs less.

I suppose it would have an affect on performance that 2 of the 3 JB drives would be on the same channel (woo, I read the FAQ! :wink: ), since the card I can afford and would get has two channels.

Rediculous as it sounds to some of you -- storage space is not an issue. I use my system for gaming and programming as well as simple web tasks, and currently my 80gb drive is nowhere near full. The slightly smaller size of a 2x raptor array would present no problem, and the much larger size of the 3xJB array would just be unused for the time being.

Also a factor worth looking at is that SATA cables are so deliciously small and compact.. and enough IDE cables for those three JBs plus my two optical drives would get kinda messy. However, I think I can live with that, if the performance is equal to or better than that of the raptors.



Out of curiosity, semi-unrelated, for someone like me who's main use for performance is in gaming (since other than that all I really do is programming and web surfing, which don't take much performance), what stripe size would you guys reccomend?


Thanks in advance for your help :smile:

-Col.Kiwi
 

lunitic

Distinguished
Aug 6, 2003
214
0
18,680
Interesting question.

I doubt whether a 3-drive setup would offer a better performance than a 2-drive setup (when using a 2-channel controller). The bandwidth is not a bottleneck here, but the fact that IDE doesn't support 'overlapped IOs' on a single channel. So you might as well stick to a 2-drive JB setup.

As for your question, 2 raptors in RAID 0 would undoubtedly outperform 2 JB's.
However, is your HD a bottleneck? Certainly not for programming or browsing. I'm not into games and I don't know what games you play, but I can't imagine the harddisk to be a bottleneck: any decent game programmer would load as much time-critical code or data in RAM as possible (but as I said: I'm no into gaming).

If I were you I would first consider buying a second (fast) harddisk, run Windows from one and your game(s) from the other. If the HD then still is a bottleneck you could buy the RAID controller and a second harddisk and start striping. Or you could buy a 4-channel controller and start striping 3 or more HD's. Or start SCSI, but that's expensive though...

Running all IDE cables can be a nuisance. You could buy rounded cables (I never took the trouble), but there is some debate about decreased performance (I don't believe that to be true, at least under normal circumstances).

The optimal stripe size depends on the type of access. Large sequential accesses benefit from a large stripe size; small random accesses benefit from a smaller size. Even a single application may have both types of access, thus some functions may gain and others may lose some performance from a larger/smaller size. In most cases the gains will be minimal though (sorry!)
 

Col_Kiwi

Distinguished
Aug 8, 2002
429
0
18,780
Yes, indeed any competant game programmer writes precache routines to load all time-critical data into RAM.

However, this means that as each game is beginning, there is a waiting period ("load time") with nothing but a progress bar and waiting :wink:

So it is related..

I also forgot to mention (it was late at night :wink: ) that I do some 2d graphics work. It's not the main use for my machine, but it exists nonetheless, and that's something where a faster disk setup helps too.

Interesting what you said about the two drives on a channel issue, I was beginning to wonder if that'd be the answer.

Theoretically -- if each was on it's own channel, how do you think a 3xJB setup would perform compared to the 2x raptor setup?

-Col.Kiwi
 

molior

Distinguished
Jul 31, 2003
44
0
18,530
Speaking from exprence of SCSI RAID0 of 7k2 & 10k rpm drives I'd say they 2x10k's will walk all over 3x7k2's. Unless you're going to be doing something which requires long sustained disk ops then the 10k's will be segnficantly faster. Simply the 7k2 drives can't compete with a 10k drive in terms of seek times, and this is the reason that even 1 Raptor will feel faster than 3x7k2 drives most of the time.

One thing you might look into is SCSI drives as, in the UK atleast, there are some very cheap 10k rpm Maxtor badged Quantum & IBM SCSI drives kicking (retailing at ~70% the cost of the WD Raptors).

Row like mortals, think like gods.
 

lunitic

Distinguished
Aug 6, 2003
214
0
18,680
I agree with molior: 2x raptor@10k rpm will outperform 3x JB@7k2 with random access, where seek times are important. For long sequential accesses the difference is different. In http://www4.tomshardware.com/storage/20030501/wd360-06.html#benchmark_results the raptor puts out 42-68 MBps, the JB (200GB version) puts out 32-56 MBps; so 2x raptor = 84-136MBps, 3xJB = 96-168 MBps, thus faster. However, this is pure theoretical: a 133 MBps PCI bus will become the new bottleneck (unless you have a 266 MBps system)
 

molior

Distinguished
Jul 31, 2003
44
0
18,530
Well after some time with a Promise TX4000 & a Dual AMD MP2000+ on a mobo with and effective 32bit/66MHz PCI bus (PCI 64/66MHz) I found* the SDR gain was about +80% of drive performence for the 2nd drive, +60% for the 3rd & +50% for the 4th which means..
2x WD Raptor's = 76~122MB/s
3x WW Caviar SE's = 77~135MB/s


* this may have been an anomoly of my machine setup but it's the only exprence ATA RAID I've have.

Row like mortals, think like gods.