I/O density ?

Question

Hi,, buddy: so what is I/O density?  it  because this section said                                                                                                                                               'For a single disk drive, various disk vendors provide the disk specifications on their Internet product sites. Since the access times for the Fibre Channel disks (not FATA) are the same, but they have different capacities, the I/O density is different. 146 GB 15k RPM disk drives can be used for access densities up 1 I/O/GBps. For 73 GB drives, the access density can be 2 I/O/GBps and for 300 GB drives, it is 0.5 I/O/GBps. While this discussion is theoretical in approach, it provides a first estimate. It is important when sizing a storage subsystem; you should not only consider the capacity but also the number of disk drives needed to satisfy the performance requirements. '  ,,,  so that means lower capacity has better performance ?

christopher_ime · Accepted Answer

With all else being equal such as mechanics, rated RPM (angular velocity), controller, cache, physical location on the platter (in consideration of linear velocity), etc., when comparing 2 otherwise identical drives, then differences in density can make a difference as more bits can be read as the drive head passes over the platter.

liulei_it · Answer

The page 16 ,

AnkitMehta · Answer

Hi lei liu,

We would love to answer your queries with regards to Performance on EMC Products. IMHO, IBM Technical Support or Support forums will be the best group who can answer performance realted questions for IBM DS8000.

Ankit Mehta

EMC Unified Storage Performance Expert/GURU.

liulei_it · Answer

thank you  , for they eaid , the smaller capacity would be better performance ?  confuse me.

liulei_it · Answer

Thanks a lot. The more bits makes better, But for example. We had had 73GB FC disk, 146GB FC disk and 300GB FC disk. then for more bits, we need to choose 73GB FC disk instead of the more capacity ?

liulei_it · Answer

Thanks ，I seem know it

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