Platters, partitions, and performance. Relation?

[chem]

Hello,

I'll soon be building a system around a WD 640gb Caviar Black, which is a 2-platter drive. It will be dual booting WinXP and Linux, so I'll need to partition it. I'm concerned that something like a 50/50 split will degrade performance in each OS. What determines which data is stored on which platter? The firmware? The partitions? If one OS is all on one partition, will this negatively affect performance?

Basically I'm worried that, say, all the WinXP partition will end up on the same platter of the drive, and this will have a bad effect on access times or read/write rates. However, I'm far from a hard drive expert, so I don't know: a. if this would even happen, and b. if it did, if performance would take a noticeable hit.

Any hard drive experts out there have experience with this kind of thing? Anyone have benchmarks?

Thanks!

 

[jcolby]

AFAIK the drive processor determines the mapping of physical space to logical space, and data is written starting on (for example) the top platter, then the underside of the top platter, then the top of the second platter, then the underside of the 2nd platter etc.

The OS has no control over this. The OS requests X sectors to create a partition and the disk controller assigns those sectors to the physical media in the manner it is programmed to. So what will happen is that (unless you make a partition of only a gig or probably even less) each partition will occupy areas starting on the outer edge of the disk and working inward. Thus whichever OS gets the first partition would be "fastest", with the second partition being next fastest.

There is more to it than that, there are "zones" on the disk, and two partitions may in fact be in the same zone (and thus the same speed), particularly if the disk is large and the partitions small.

I am not a disk expert, and I do not play one on TV.

 

[Joe Average]

The platters aren't broken down as separate storage devices; the drive works as a whole medium based on the capacity of the drive.

We're not talking about 15 years ago, with 4200 rpm hard drives with 512KB buffers being all the rage where drive performance actually mattered depending on where the data sat on the drive.

That WD 640GB is arguably one of the fastest non-Raptor/non-Velociraptor/non-SCSI/non-Fiber-Channel/non-SSD/etc drives ever manufactured. It doesn't matter - realistically - where you put Windows or Linux on it, be happy that the shit will be fast, period.

You're talking about the difference between what, 100MB/s average read speeds at the very beginning of the drive and maybe 85-90MB/s near the end, it's simply irrelevant in the big picture and you really should stop worrying about such a thing. The differences are simpl inconsequential in day to day operation.

If you want the fastest setup for both OSes, install Windows to a set partition size and then put the Linux (with a swap) partition immediately after it and go from there, using the remaining space on the drive as secondary partitions for data storage as required (meaning NTFS or Ext2/3, etc).

Just checking but, you do realize that WD 640GB is highly regarded because it is so damned fast, right?