looking for specs on 72, 146, and 300GB disks

[Hanry Zhou]

We have XP12000 XP frame, and wanted to evaluate on what disks we should add in for the space expansion. currently we have 72/146GB.

I am looking for data about how many heads, how much cache, and i/o per seconds, all these kind of data. Where I can find them?

Thanks,

[Torsten.]

All of this is IMHO very much meaningless, because the controllers do all the I/O and caching from host point of view.

[Torsten.]

Some values are here:

http://h18000.www1.hp.com/products/quickspecs/12072_div/12072_div.html

[Hanry Zhou]

Torsten,

Your input is very helpful, and you are makding good points.

Would you please elaborate more on what you said "the controllers do all the I/O and caching from host point of view.", why we don't need to worry about too much on these paramers we are looking for?


Also, anywhere else I could get the data on how many heads, how much cache, and i/o per seconds on these 72, 246, and 300GB disks. I am sorry, I just have to get back them on these data.

Thanks,

[Torsten.]

There are many many options to boost performance in this kind of arrays. You can for example configure LUNs to be handled in cache completely or spread across many disks. If data is completely handled in cache, the real disk speed doesn't matter at all, would you agree? There are a lot of options how to bring data into the cache, hold them there or write them back.
This cannot be explained so easily, because it's very complex. Best would be to discuss this with your HP representative.

But think about this, with an amount of around 256 GB cache and cache bandwidth of up to 68 GB/s you can handle a lot of data.

As said, many options, all depend, but surely not only on disk characteristics.

[Hanry Zhou]

Torsten,

Please bear with me...

I understand how XP would perform well in some degree. However, I am still trying to figure out how that would play down the importance of the disk itself perofmrnace. Folks here still emphasize on the individual disk.

I understand you correctly, because of SAN/Fibre Channel technology, unlink traditional SCSI world, the performance on individual disk is not a big issue, the components to determine the performance will be on FC port speed, amount of cache size, chips on DKA/DKC controllers..etc. The disk itself will not become the bottleneck on the performance.

would that be right understanding?

Thanks for your help.

[Hanry Zhou]

On the same question, could anybody else provide the information for me? As far as if 72G and 300GB make any performance difference in a XP 12000K environment? they both got 15Krmp speed.

Thanks,

[Hanry Zhou]

Would it be true that smaller size of disks, better in the perfornace, and therefore 73gb would be better than 300GB?