sub mesa :
The data is not redundant on RAID0, so it cannot choose which disk it wants to read from because that disk has its head is closest to the desired data track. As for access times: with a stripe misalignment you will loose much of the parallel operation RAID0 can offer, and is common with people using Windows. In fact virtually all RAID-arrays have a misalignment with the filesystem, causing lower performance. But it usually only affects IOps and access times, not throughput, that's why people wrongfully assume RAID increases access times or that it only increases throughput and not IOps performance.
I know RAID 0 is not capable of the multiple simultaneous reads or greatly improved seek times due to positioning that RAID 1 allows ( I actually prefer RAID 1 for an OS specifically for these performance benefits over RAID 0 ). However, the actual staggered position of the drive heads after time on a RAID 0 due to file sizes not filling the entire stripe WIDTH, does marginally improve random access times. If the random reads/writes are smaller than the actual stripe SIZE, then greater seeks AND IO can be achieved, albeit at a random gain from positioning ( this is true for all RAID levels ). This "stripe misalignment" you refer to is just a natural occurence in any RAID level other than bit level striping which require all heads to be synched at all times. Byte level striping does not have this restriction, thus having no real "stripe misalignment" to be concerned over. RAID 5 is the best example of this phenomenon, as sequential performance is greatly reduced as the array is filled with data not just because of the slower areas of the HDD's, but also from the increased staggered drive head positioning. All byte-level RAID sets have the potential to increase IO. These are not vague assumptions, but readily available facts. I have 4x 14 drive SCSI arrays ( along with smaller SATA/SAS arrays ) that I've done exhaustive testing and benchmarking with ALL RAID levels. The wrong assumption on seek times or IO usually result from starting with SATA drives with poor native seek times to begin with, mobo or very low end controllers, and poor partitioning stratagys. The actual RAID level should not be faulted.
With that being said, I still see no reason for a single 4 drive RAID 0 in the OP's case. 1 2x RAID 1 or 0 for the OS, and 2x RAID 1 or 0 for programs or storage would yield better system performance. With 4 drives, this could be a possible config.....
2x 160GB
RAID 1......160GB total, partitioned as....
C: windows ( along with A/V and and any other system related tools i.e. nero ) 30GB partition
This gives the multiple simultaneous read performance RAID 0 does not provide along with improved random seek times. Your A/V and OS will appreciate this more than a RAID 0 in most cases, although benchmarking will not show this value unless queue depth is increased. Superior to RAID 0 for multi-tasking.
E: Storage ( Set-up files, drive images, Important files, My Docs ) 130GB partition
The simple mirroring of RAID 1 gives you DATA security here for the stuff you don't want to lose. If imaging your OS drive, make sure to output it to the "F" partition first, then copy it to the "E" partition to reduce drive head contention. Moving My Docs here also saves on fragmentation to your system disk.
2x 160GB
RAID 0......320GB total, partitioned as....
D: Programs ( all large programs such as games, office, or whatever ) 60-120GB partition depending on requirements
Using RAID 0 here will improve load times for the large apps/games as well as providing some IO improvement.
F: Scratch disk ( all the files you don't mind losing or have backed-up elsewhere ) remaining 240GB )
The increased sequential speeds make this partition nice for media files already backed-up on DVD's. This partion should also be used as your working partition for any transcoding and such as the programs for that behavior are located on a completely different RAID array ( drive "C" ), further reducing drive contention.
I usually prefer a 3 logical drive set-up as opposed to this 2 logical drive set-up, as contention for "My Documents" can exist. This can be reduced by placing programs which access these files regularily on the D partition. If using XP with a mild amount of RAM, then swap file placement can be important here also. After a fresh install, remove the swap file from C: and create one on the empty D: partion using a fixed size. Re-Boot, run a couple of defrags ( I prefer DiskTrix Ultimate Defrag, as it allows direct control over file placement on the physical HDD's.....learn it, use it, love it ). Now Re-create the swap file on C: again using a fixed size. Having a swap file on both drives will be very beneficial in lower RAM situations. Windows XP does a great job of intelligently managing multiple swap file locations i.e. a program running on C: will use the swap file on D: and vise-versa.
The most common mistake I see is people forgetting that sequential reads and writes are only as good as the destination or source when doing file management ( a weakest link scenario ). Load times will be improved by the reads, but unless your other drives/arrays are capable of these high speeds you won't gain anything.
Hope this essay long post helps........
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