I found this very interesting since it clearly indicates that modern
large hard drives do take advantage of linear data density by putting
more data on the outer tracks. Placing sequentially accessed data there
minimizes rotational delay. But faster *seek* times for data in the
center is why the Windows directory has been there since Windows NT.
The rest of your comments are interesting with respect to large capacity
servers but most of us don't have such things in our houses.
Chuck Norcutt
On 8/15/2012 3:00 AM, SwissPace wrote:
> As someone who used to get paid for this sort of thing (database
> performance tuning) it did make a difference, I would however agree that
> on a modern windows systems with modern large disks it would make little
> difference. It's really amazing how much things have changed in recent
> years.
>
> For those who want to know
>
> this was taken from
> <http://www.ibm.com/developerworks/aix/library/au-aixoptimization-disktun2/index.html>
>
> *Figure 2. Actual storage position on the physical disk platter*
> Actual storage position on the physical disk platter
>
> As a general rule, data that is written toward its center has faster
> seek times than data written on the outer edge. This has to do with the
> density of data. Because it is more dense as it moves toward its center,
> there is actually less movement of the head. The inner edge usually has
> the slowest seek times. As a best practice, the more intensive I/O
> applications should be brought closer to the center of the physical
> volumes. Note that there are exceptions to this. Disks hold more data
> per track on the edges of the disk, not on the center. That being said,
> logical volumes being accessed sequentially should actually be placed on
> the edge for better performance. The same holds true for logical volumes
> that have Mirror Write Consistency Check (MWCC) turned on. This is
> because the MWCC sector is on the edge of the disk and not at the center
> of it, which relates to the intra-disk policy of logical volumes.
>
> Let's discuss another important concept referred to as the inter-disk
> policy of logical volumes. The inter-disk policy defines the number of
> disks on which the physical partitions of a logical volume actually
> resides. The general rule is that the minimum policy provides the
> greatest reliably and availability, and the maximum policy improves
> performance. Simply put, the more drives that data is spread on, the
> better the performance. Some other best practices include: allocating
> intensive logical volumes to separate physical volumes, defining the
> logical volumes to the maximum size you need, and placing logical
> volumes that are frequently used close together. This is why it is so
> important to know your data prior to configuring your systems so that
> you can create policies that make sense from the start.
>
>
>
> On 14/08/2012 21:33, Jim Nichols wrote:
>> Hi Chuck,
>>
>> With modern, large drives, I have seen no improvements in the rare occasions
>> I have run a defrag program. And, with the increase in drive capacities, it
>> would take forever to complete a defrag effort. I agree, snake oil!
>>
>>
>
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