Re: Power7 / Power8 internal disk differences - future disk planning

See in line comments.

- Larry "DrFranken" Bolhuis

www.Frankeni.com
www.iDevCloud.com - Personal Development IBM i timeshare service.
www.iInTheCloud.com - Commercial IBM i Cloud Hosting.

On 12/6/2017 4:38 PM, Steinmetz, Paul wrote:

Larry,

1) My current SSD are ES0H, announced November 2013 - IBM i 7.1 Technology Refresh 7 and IBM i 6.1 Additional Enhancements.

775 GB SFF SSD with eMLC (#ES0E, #ES0F, #ES0G, #ES0H) The new 775 GB SFF SSD, using the same technology as the new higher performance 387 GB disk drive, doubles the capacity that can fit in a single slot. IBM i support is provided for both POWER7 and POWER7+ servers, and for both IBM i 7.1 and IBM i 6.1 with 6.1.1 machine code.

The documentation doesn't always include if they are 5XX or 4K.
How does one determine this?
I'm using FC #5913, so from your previous post below, I'm concluding they are 5XX.

Yes that is correct those are 5xx. Normally if they do not specify they are 5XX if they specify they will say 4K.

2) Will these ES0H disks work on Power8 in an EXP24S, or possibly Power9 with an EXP24S or EXP24SX.

Yes to Power8 in an EXP24S but if they are in the system unit today they will need new sleds to fit in there. Since you are using 5913 I expect they are in SFF-2 sleds today so that will work.

'Likely' to Power9 BUT because that stuff isn't announced yet we cannot be certain.

3) Based on your previous post, (4K Disks they are better because they cut the number of I/Os by 8)
For future planning, we should get rid of the 5XX and plan on using 4K, correct?

Indeed. And you also get a refreshed warranty on the new drives as well so that's a big money saver with SSDs. Despite the lower number of raw I/Os the amount of data moved isn't significantly lower so actual performance gains are minimal. However all disks are moving to 4K Block going forward and I would guess at some point IBM i will drop support for 5XX block disks.

4) With that said, future planning for disks.

Production - for top performance
#ES8D - 775GB SFF-2 SSD 4k eMLC4 for IBM i
#ES8G - 1.55TB SFF-2 SSD 4k eMLC4 for IBM i
#ES8R - 775GB SFF-3 SSD 4k eMLC4 for IBM i
#ES8W - 1.55TB SFF-3 SSD 4k eMLC4 for IBM i

R&D - improvement over current 10K spinny, but using the cheaper SSD.
#ES84 - 931 GB Mainstream SAS 4k SFF-3 SSD for IBM i
#ES8Z - 931 GB Mainstream SAS 4k SFF-2 SSD for IBM i
#ES93 - 1.86 TB Mainstream SAS 4k SFF-3 SSD for IBM i
#ES97 - 1.86 TB Mainstream SAS 4k SFF-2 SSD for IBM i
#ESE2 - 3.72 TB Mainstream SAS 4k SFF-3 SSD for IBM i
#ESE8 - 3.72 TB Mainstream SAS 4k SFF-2 SSD for IBM i

"Improvement over 10K spinny." Yes it will!! There's your candidate for 'understatement of the year'. :-)

5) However - I did read this link that scares me a bit with the performance of large SSD drives, especially if they are Mainstream.

An interesting question about SSD performance scaling with size

https://www.ibm.com/developerworks/community/blogs/svcstorwize/entry/An_interesting_question_about_SSD_performance_scaling_with_size?lang=en

An interesting read! The biggest issue I think for IBM i is doing something silly like getting two massive SSDs and mirroring them. Problem is that IBM i wants arms and even these incredibly fast arms are held back by IBM i and shallow I/O queues. Plus the big drives are more bucks per TB at this point and you will have slots anyway sooooo get a half dozen at least, perhaps 8 and now everyone is happy!

Any thoughts from the group?

Paul


-----Original Message-----
From: DrFranken [mailto:midrange@xxxxxxxxxxxx]
Sent: Monday, December 04, 2017 5:42 PM
To: Midrange Systems Technical Discussion; Steinmetz, Paul
Subject: 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.


- Larry "DrFranken" Bolhuis

www.Frankeni.com<http://www.Frankeni.com>
www.iDevCloud.com<http://www.iDevCloud.com> - Personal Development IBM i timeshare service.
www.iInTheCloud.com<http://www.iInTheCloud.com> - Commercial IBM i Cloud Hosting.

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



Thank You
_____
Paul Steinmetz
IBM i Systems Administrator

Pencor Services, Inc.
462 Delaware Ave
Palmerton Pa 18071

610-826-9117 work
610-826-9188 fax
610-349-0913 cell
610-377-6012 home

psteinmetz@xxxxxxxxxx<mailto:psteinmetz@xxxxxxxxxx>
http://www.pencor.com/