Re: [suggestion]Is writing relay log necessary in slave?

[feng guo]

Rick James Wrote:
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> There are potentially two replication-related logs
> on a Slave:
>
> * The "relay_log(s)" are absolutely required --
> they hold the stuff sent from the Master's
> "binlog(s)". Yes, it is a staging area, but
> usually it involves nearly zero overhead. If
> replication gets behind, then it becomes a safety
> measure -- things can be sent from the Master to
> the relay_log rapidly even if they cannot be
> executed immediately. That way, if the Master
> dies, there is less risk of any loss on the Slave.
> ("Semi-Sync" adds safety to this.)
>
> * The binlog (on a Slave) is optional. It is the
> same concept as the Master's binlog -- namely it
> holds the writes. It is useful for
> ** Various backup things; incremental backups;
> etc
> ** Having a Slave hanging of this Slave -- a more
> complex topology of servers.
> ** Dual-Master -- two servers, each being both a
> Master and a Slave to each other.
>
> Your comments/suggestions are focused on the
> Slave; the relay_log is focused on keeping the
> Master going.
>
> > master's binlog file name and position to an
> transaction safe table
>
> This, and similar things that are currently kept
> in files, may be coming soon in version 5.7. The
> design is a tricky problem of chicken-and-egg
> and/or runaway allocation and/or "transaction
> safe".
>
> > avoid slave disk's relay log writing load
>
> Check it out -- I rarely see more than 2GB of data
> going into a relay_log per _day_. How much do you
> have? 2GB/day is not much burden on a disk
> system. The LAN/WAN will probably be overloaded
> before the disk.

Thx,relay log is really necessary~