[Gluster-users] ec heal questions

Ashish Pandey aspandey at redhat.com
Mon Aug 8 11:48:20 UTC 2016


Heal for 2 different files could be parallel but not for a single file and different chunks. 
I think you are referring your previous mail in which you had to remove one complete disk. 

In this case heal starts automatically but it scans through each and every file/dir 
to decide if it needs heal or not. No doubt it is more time taking process as compared to index heal. 
If the data is 900GB then it might take lot of time. 

What configuration to choose depends a lot on your storage requirement, hardware capability and 
probability of failure of disk and network. 

For example : A small configuration like 4+2 could help you in this scenario. You can have distributed disp volume of 4+2 config. 
In this case each sub vol have a comparatively less data. If a brick fails in that sub vol, it will have to heal only that much data and that too from reading 4 bricks only. 


subvol-1 subvol-2 subvol-3 
4+2 4+2 4+2 
4GB 4GB 4GB 
If a brick in this subvol-1 fails, it will be local to this subvol only and will require only 4GB of data to be healed which will require reading from 4 disk only. 

I am keeping Pranith in CC to take his input too. 


----- Original Message -----

From: "Serkan Çoban" <cobanserkan at gmail.com> 
To: "Ashish Pandey" <aspandey at redhat.com> 
Cc: "Gluster Users" <gluster-users at gluster.org> 
Sent: Monday, August 8, 2016 4:47:02 PM 
Subject: Re: [Gluster-users] ec heal questions 

Is reading the good copies to construct the bad chunk is a parallel or 
sequential operation? 
Should I revert my 16+4 ec cluster to 8+2 because it takes nearly 7 
days to heal just one broken 8TB disk which has only 800GB of data? 

On Mon, Aug 8, 2016 at 1:56 PM, Ashish Pandey <aspandey at redhat.com> wrote: 
> Hi, 
> Considering all the other factor same for both the configuration, yes small 
> configuration 
> would take less time. To read good copies, it will take less time. 
> I think, multi threaded shd is the only enhancement in near future. 
> Ashish 
> ________________________________ 
> From: "Serkan Çoban" <cobanserkan at gmail.com> 
> To: "Gluster Users" <gluster-users at gluster.org> 
> Sent: Monday, August 8, 2016 4:02:22 PM 
> Subject: [Gluster-users] ec heal questions 
> Hi, 
> Assume we have 8+2 and 16+4 ec configurations and we just replaced a 
> broken disk in each configuration which has 100GB of data. In which 
> case heal completes faster? Does heal speed has anything related with 
> ec configuration? 
> Assume we are in 16+4 ec configuration. When heal starts it reads 16 
> chunks from other bricks recompute our chunks and writes it to just 
> replaced disk. Am I correct? 
> If above assumption is true then small ec configurations heals faster right? 
> Is there any improvements in 3.7.14+ that makes ec heal faster?(Other 
> than multi-thread shd for ec) 
> Thanks, 
> Serkan 
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> Gluster-users mailing list 
> Gluster-users at gluster.org 
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