[gpfsug-discuss] Flash for metadata

[Richard Welp]

I checked with the FS900 performance expert in Tucson, and here is what I 
was told:

The 4KB and 512B blocks will both get equally great sub millisecond 
response times but 4KB can achieve a higher maximum IOPS rate.

As far as # of luns,  it doesn't really matter to the FS900, but the host 
operating system and other components in the data path can benefit from 
having more than 1 large lun.  If we are trying to get the maximum 
possible iops, we typically run with at least 16 luns.    I suspect with 4 
luns you would get within 10% of the maximum performance. 

Thanks,

Rick

===================
Rick Welp
Software Engineer
Master Inventor
Email: rwelp at uk.ibm.com
phone: +44 0161 214 0461 
IBM Systems - Manchester Lab
IBM UK Limited 
--------------------------




From:   "Marc A Kaplan" <makaplan at us.ibm.com>
To:     gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:   19/05/2016 11:00 pm
Subject:        Re: [gpfsug-discuss] Flash for metadata
Sent by:        gpfsug-discuss-bounces at spectrumscale.org



"I assume that creating several smaller LUNs on each FlashSystem in the 
same failure group is still preferable to one big LUN so we get more IO 
queues to play with?"

Traditionally, more spindles, more disk arms working in parallel => better 
overall performance.

HOWEVER Flash doesn't work that way... So it's going to depend... 
Perhaps some kind soul can point us to some information about this and how 
much it varies among today's flash based storage products.
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