Hello Michael,
On 2015-05-15 10:58, Prof. Dr. Michael Schefczyk wrote:
Basically, I am looking for a smart model to run the system in a
virtualized environment. The hypervisor is KVM on Centos 7. I use the
standard caching (writeback) for the guest disk and no cache for nfs.
The nfs connection is over 10Gb/s Ethernet which is just used for
connecting two hypervisors to one NAS. The utilization of the overall
system is rather low - far away from congestion.
Space of the mailpiler DB is not a real issue. In my case, it consumes
ca. 2 GB with automysql backup files. What I like to do, however, is
to use guest machines with small disks (i. e. less than 16 GB) which
permit a swift nightly live backup. Under those circumstances,
separating the mysql files sounded (and sounds) like a good idea to
keep the system scalable. In case I needed to revert the guest machine
to a state of a few days ago (this does not happen often), the current
database files including its backups would still be there. This does
seem to work well with clean shutdowns, but not with unfriendly
shutdowns.
My practical experience is, that unfriendly shutdowns are no issue if,
(a) the database files are on the virtual guest disk itself (but at
the cost of not getting the advantages stated above) or (b) using
MyISAM, which I noted after converting from InnoDB to MyISAM on my
virtualmin web server (with the bad feeling that InnoDB is the storage
engine in the focus of future development).
To resolve the issue with mailpiler, I do consider the following
options:
1. Change caching model.
2. Move to iSCSI.
3. Move away from nfs by providing a second virtual disk to the guest,
containing just the database files.
4. Convert to MyISAM storage engine.
My feeling is to try 3) first and 4) second. Do you have
recommendations for me?
I'd still recommend you to use a dedicated sql host with local disk(s).
In addition, I am considering to move the mailpiler DB to a separate
server along with my other databases. Of course this does only
centralize the issue so the basic problem still remains. Is it as
simple as changing the 'localhost' parameter in config.php and making
the database available at the new location?
yes, however don't forget to fix piler.conf as well, then restart piler.
Janos
