[Gluster-users] disperse volume brick counts limits in RHES

[Xavier Hernandez]

On 05/05/17 13:49, Pranith Kumar Karampuri wrote:
>
>
> On Fri, May 5, 2017 at 2:38 PM, Serkan Çoban <cobanserkan at gmail.com
> <mailto:cobanserkan at gmail.com>> wrote:
>
>     It is the over all time, 8TB data disk healed 2x faster in 8+2
>     configuration.
>
>
> Wow, that is counter intuitive for me. I will need to explore about this
> to find out why that could be. Thanks a lot for this feedback!

Matrix multiplication for encoding/decoding of 8+2 is 4 times faster 
than 16+4 (one matrix of 16x16 is composed by 4 submatrices of 8x8), 
however each matrix operation on a 16+4 configuration takes twice the 
amount of data of a 8+2, so net effect is that 8+2 is twice as fast as 16+4.

An 8+2 also uses bigger blocks on each brick, processing the same amount 
of data in less I/O operations and bigger network packets.

Probably these are the reasons why 16+4 is slower than 8+2.

See my other email for more detailed description.

Xavi

>
>
>
>     On Fri, May 5, 2017 at 10:00 AM, Pranith Kumar Karampuri
>     <pkarampu at redhat.com <mailto:pkarampu at redhat.com>> wrote:
>     >
>     >
>     > On Fri, May 5, 2017 at 11:42 AM, Serkan Çoban
>     <cobanserkan at gmail.com <mailto:cobanserkan at gmail.com>> wrote:
>     >>
>     >> Healing gets slower as you increase m in m+n configuration.
>     >> We are using 16+4 configuration without any problems other then heal
>     >> speed.
>     >> I tested heal speed with 8+2 and 16+4 on 3.9.0 and see that heals on
>     >> 8+2 is faster by 2x.
>     >
>     >
>     > As you increase number of nodes that are participating in an EC
>     set number
>     > of parallel heals increase. Is the heal speed you saw improved per
>     file or
>     > the over all time it took to heal the data?
>     >
>     >>
>     >>
>     >>
>     >> On Fri, May 5, 2017 at 9:04 AM, Ashish Pandey
>     <aspandey at redhat.com <mailto:aspandey at redhat.com>> wrote:
>     >> >
>     >> > 8+2 and 8+3 configurations are not the limitation but just
>     suggestions.
>     >> > You can create 16+3 volume without any issue.
>     >> >
>     >> > Ashish
>     >> >
>     >> > ________________________________
>     >> > From: "Alastair Neil" <ajneil.tech at gmail.com
>     <mailto:ajneil.tech at gmail.com>>
>     >> > To: "gluster-users" <gluster-users at gluster.org
>     <mailto:gluster-users at gluster.org>>
>     >> > Sent: Friday, May 5, 2017 2:23:32 AM
>     >> > Subject: [Gluster-users] disperse volume brick counts limits in
>     RHES
>     >> >
>     >> >
>     >> > Hi
>     >> >
>     >> > we are deploying a large (24node/45brick) cluster and noted
>     that the
>     >> > RHES
>     >> > guidelines limit the number of data bricks in a disperse set to
>     8.  Is
>     >> > there
>     >> > any reason for this.  I am aware that you want this to be a
>     power of 2,
>     >> > but
>     >> > as we have a large number of nodes we were planning on going
>     with 16+3.
>     >> > Dropping to 8+2 or 8+3 will be a real waste for us.
>     >> >
>     >> > Thanks,
>     >> >
>     >> >
>     >> > Alastair
>     >> >
>     >> >
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>     >
>     >
>     >
>     > --
>     > Pranith
>
>
>
>
> --
> Pranith
>
>
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