Re: Power7 / Power8 internal disk differences

Yes and no.

Physically the disks in the Power7 CEC are in slightly deeper and slightly taller sleds than those in Power8 CEC disks. However the disks could be resleded and used in the new system as the actual disks themselves are compatible.

As for the 4K Disks they are better because they cut the number of I/Os by 8. Now IBM i has used 4K has a block size since the CISCO to RISC migration years ago but has always had to write 8 520Byte sectors to handle that. (Whether they only update 1 of the 8 if a very small update is performed within the block I do not know.)

Tracking what needs to be updated should be simpler with 4K Block disks and they are pretty much the standard in the industry now. With them you can address 8 times the storage that you could with 520 byte sectors using the same number of addresses.

To use 4K Block disks you need PCIe Gen3 RAID cards or newer on Power Systems. So for example FC #5913 or FC #ESA3 controllers will NOT recognize 4K Disks. FC #5887 disk drawers work fine with either 4K or 520 byte disks.

Power8 CECs can have 520 or 4K Block disks in them.


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On 12/4/2017 4:47 PM, Steinmetz, Paul wrote:

1) Are Power7 and Power8 internal disks different?

2) What is difference between the 5XX and 4k disks, which is better, and where are they used?

https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/IBM%20i%20Technology%20Updates/page/IBM%20i%20IO%20Support%20Details



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