Single IDE vs Dual IDE?

jrsimmons asks: "I'm running performance tests on IDE interface configurations for my company. I've discovered that disk to disk I/O is significantly faster (in the realm of 30%-40%) when only a single IDE interface is active versus when two IDE interfaces are active. This is significant as our servers are used to provide Point-of-Sale availability for registers in the retail environment, which is heavily dependent on disk i/o performance for efficiency. I have run the tests under both Windows and our retail OS (sorry, no Linux) with similar results. What are some possible explanations for the detrimental effect the second active ide controller has on disk I/O speed?" Has anyone measured this deficiency on Linux and other Unices?

Comments

Sounds strange

[Outland Traveller]

Your results sound strange to me.

For two disks, you should get the best results with both disks configured as masters on two different IDE buses.

If you're not seeing that, I'd check that you have the correct drivers/optimizations for your IDE chipset enabled. You also might want to check IRQ allocation to make sure there's no strange conflicts . Check your windows (NT/2000) event log to make sure there's no strange IDE timeouts indicating hardware issues. If you still see the problem you should try your test on a different hardware platform (motherboard/controller combo).

From your description, however, you might want to go with a raid technology such as RAID 1, RAID 5, or raid 1+0. It will offer much better redundancy and possibly improved performance.

Hang On.. Give Some Info.

[His name cannot be s]

What exactly do you mean by active? There are two drives on one IDE interface? Two Drives, one on each interface? One Drive, And both interfaces turned on in the BIOS?

I'll take for granted that you actually have a good way of measuring drive performance, and it's not just a 'feeling'.

What motherboard/Chipset/PC's are you talking about here? Have you replicated the results on dissimilar hardware?

What was significance of the second active ide controller? were you moving data to two drives?

And finally, Why is your system sooooo dependant on disk I/O? If this is the case, mayhap you need to re-engineer the app somewhat to balance out the disk IO aspect. If it's actually CONSTANTLY saturating one or two IDE channels, Quit being a complete twit, and move to SCSI, where this isn't a problem.

If you actually want help on this, you had better provide a heck of alot more information up front.

G

I'd guess...

[Polo]

I'd guess one or both of the drives is not in DMA mode. It's probably configured as PIO mode.

This is a pretty common mistake - if the drive is in PIO mode, all i/o goes through the cpu.