[Users] VE affecting all server node.

[Solar Designer]

On Tue, Feb 23, 2010 at 08:29:02AM -0800, Gregor at HostGIS wrote:
> Questions: Can I mount a tmpfs under my simfs?

Yes, and you should always be doing that.  For example, our pre-created
container templates of the Openwall GNU/*/Linux userland, which I
announced in here a while ago, contain this line in /etc/fstab:

tmpfs		/tmp			tmpfs	nosuid,nodev		0 0

You may also mount additional instances of tmpfs and control their size,
owner, and permissions with additional mount options.  For example, you
may add:

tmpfs		/tmp-b_user		tmpfs	nosuid,noexec,nodev,uid=b_user,gid=b_user,mode=700,size=4G	0 0

(a real example from a production server, with only the username replaced).
Indeed, this server has a lot more than 4 GB of RAM, and in fact this
container is allowed to allocate significantly more than that too, which
is why limiting this tmpfs mount size to 4 GB made sense.  You will need
to adjust this to match your setup.

> I can't mount the whole VPS as tmpfs

This would be undesirable most of the time and too tricky to do
(assuming that your data is not temporary).

> nor noatime,

Why not?  We certainly have the filesystems on which /vz or portions
thereof reside mounted with noatime on many systems.

> but a tmpfs under simfs sounds like a great 
> solution here. If I can then set MySQL's tempfile directory to it, 

This is controlled with the --tmpdir=... option to mysqld.

> you're right that it could reduce our disk traffic significantly.

It depends on the nature of SQL queries.  Only some of them produce
temporary files.

I'd like to emphasize that the use of tmpfs for temporary files and the
noatime option for the rest are orthogonal - that is, it is possible and
preferable to use both at once.

Alexander