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 Post subject: Re: 3PAR OS 3.3.1 MU1 is released
PostPosted: Fri Nov 03, 2017 7:29 am 

Joined: Thu Jan 22, 2015 3:37 pm
Posts: 21
HPE confirmed they won't do any upgrades to MU1 P17. They are on hold until P18 is out. I believe this will all be rolled into an EMU1. It is supposed to be out by the middle of November. They have no problems upgrading to 3.3.1 EGA with P16...just no MU1.

On another note. Our they showed concern that I wanted to upgrade my 7440's to 3.3.1. I told them I needed greater than 16T volumes. They were concerned that I wanted to use the new dedupe on all my volumes which they say the 7k isn't the best at. Even though the new dedupe is better...it just causes real high CPU on the nodes.


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 Post subject: Re: 3PAR OS 3.3.1 MU1 is released
PostPosted: Sat Nov 04, 2017 12:50 am 
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Joined: Fri Jun 21, 2013 1:03 pm
Posts: 77
Location: USA
mitchellm3 wrote:
On another note. Our they showed concern that I wanted to upgrade my 7440's to 3.3.1. I told them I needed greater than 16T volumes. They were concerned that I wanted to use the new dedupe on all my volumes which they say the 7k isn't the best at. Even though the new dedupe is better...it just causes real high CPU on the nodes.


Any idea how high they are worrying about? I've been sitting at 15-20% utilization on a couple of 7000 series arrays.


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 Post subject: Re: 3PAR OS 3.3.1 MU1 is released
PostPosted: Mon Nov 06, 2017 2:58 am 

Joined: Thu Jun 01, 2017 1:55 am
Posts: 17
mitchellm3 wrote:
They were concerned that I wanted to use the new dedupe on all my volumes which they say the 7k isn't the best at. Even though the new dedupe is better...it just causes real high CPU on the nodes.


Dedupe is an ASICS process it should not have any impact on CPU. Compression is a CPU process which on our 8200 causes >70% CPU :?


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 Post subject: Re: 3PAR OS 3.3.1 MU1 is released
PostPosted: Mon Nov 06, 2017 3:25 am 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 454
Chris212 wrote:
Dedupe is an ASICS process it should not have any impact on CPU.


If that is the case, why does the All-flash models (xx50) have beefier CPUs in addition to memory? This is both true for the 8k/20k and the 7k which doesn't even support compression. My understanding is that the dedupe and dedupe checking etc happens in the ASICs but a lot of other processes related to dedupe doesn't (GC to mention one).


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 Post subject: Re: 3PAR OS 3.3.1 MU1 is released
PostPosted: Mon Nov 06, 2017 11:18 am 

Joined: Wed May 07, 2014 10:29 am
Posts: 134
"Dedupe is an ASICS process it should not have any impact on CPU."

Nonsense, only checksumming is done in ASIC and 3PAR does an active read/compare (in ASIC?)
so not only is dedupe high cpu, but generates additional IO as well.
Dont believe marketing, that is the first thing you should learn in IT.

I have also experienced very high CPU usage on the low end controllers,
disable dedupe and it is down to more manageable levels.

There is also an issue on v1 and v2 with dedupe TPVV where the hash table runs very large.
This is mitigated in v3 on 3PAR OS 3.3.1 but I have not tested yet.
Required migration into new CPG though...


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 Post subject: Re: 3PAR OS 3.3.1 MU1 is released
PostPosted: Tue Nov 07, 2017 5:03 am 

Joined: Wed Nov 19, 2014 5:14 am
Posts: 451
The reason more cores and more memory are beneficial is that dedupe generates a lot of metadata and the fastest way to access that metadata is if it resides in memory. The lower the available memory the more paging to/from SSD has to occur and the more backend I/O is generated. Similarly the ASIC based hashing and dedupe is only the first part of the process, in order to free space in a dedupe store you need garbage collection and if you want that to occur regularly then you need idle compute to patrol and sweep that, hence more cores are better when you want sustained performance. There's a good reason why the all flash arrays have more grunt and that's not only related to all out performance.

3PAR isn't unique in this it affects all dedupe enabled systems, although in many the processes are hidden to a certain extent since you have no comparative measures e.g. you only have a single store so no ability to change, reclaim or move space and there's typically no way to turn off the process to compare performance with and without. The fact that some systems defer the process under heavy load should tell you it's not a free process despite the marketing.


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