[Gluster-devel] Question about EC locking

[Xavier Hernandez]

Hi,

On 11/28/2016 02:59 AM, jayakrishnan mm wrote:
> Hi Xavier,
>
> Notice  that EC xlator uses blocking locks. Any specific reason for this?

In a distributed filesystem like gluster a synchronization mechanism is 
a must to avoid data corruption.

>
> Do you think this will  affect the  performance ?

Of course the need for locks has a performance impact, and we cannot 
avoid them to guarantee data integrity. However some optimizations have 
been applied, specially the eager locking which allows a lock to be 
reused without unlocking/locking again.

>
> (In comparison AFR  first tries  non blocking locks  and if not
> successful, tries blocking locks then)

EC also tries a non-blocking lock first.

>
> Also, why two locks  are  needed  per FOP ? One for normal I/O and
> another for self healing?

The only fop that currently needs two locks is 'rename', and only when 
source and destination directories are different. All other fops only 
take one lock at most.

Best regards,

Xavi

>
> Best regards
> JK
>
>
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