How to disable mirror for a faster mysql tmp volume

[jody3t]

I have a tmp vol mounted on a mysql DB appliance (local_only) and I wanted to disable mirroring for that volume to improve performance and also because the tmp vol does not really require failover and so it should reduce grid traffic (we have alot of tables with TEXT and BLOBS unfortunately so we have alot of tmp tables created).

Seems like it should be easy, but I don't see how.

Jody

[PeterNic]

Jody,

The way to do it is to specify the mirrored=0 option when creating or copying the volume. See http://doc.3tera.net/AppLogic2/CliVolume.html#AnchorCreate

Now, two caveats:
- you may not see a significant performance improvement -- the two mirrors are being written to in parallel; we have seen performance actually go up when using a remote volume (due to being able to use the CPU of the remote server -- even though the overall load on the system *is* higher)
- if you disable the mirroring for that volume, you will lose HA for the appliance -- even if you don't care for the content, if the server that holds the only copy of the volume dies, there is no automatic way to get the appliance working again without human intervention (and of a human who knows it is OK to start from a blank volume -- most support technicians will be rightfully freaked out if there is no spare mirror of the database volume)

In light of this -- what is the bottleneck you are getting? can you use ram-based storage (e.g., ramfs or tmpfs) or in-memory tables?

Regards,
-- Peter

[jody3t]

Actually there is currently no bottleneck. I just thought it might improve performance to have my tmp table vol not be mirrored (or at least not generate as much grid backbone traffic), but from what you have said I don't think it is really necessary (or would even help) and I definitely want failover for the mysql appliance.

Thanks Peter,