stability for multi-user environment ..

We have a requirement where we have to ship an offline version of our product, as well as keep an online version of it for our customers. It looks like hsqldb will hold up well for offline customers because that will be a single user environment. The question is, is it stable enough to hold up against our online users as well ? We won’t be having more than 1000 users online. Most of them will be doing reads against the database. There would be some writes. I would have to change the transaction model to MVCC. Any reason why hsqldb doesn’t default to it ?

Would it be better to use hsqldb for offline folks, but use something like mysql for the online folks who would use it over the web ? Wasn’t able to find reviews about people who have used hsqldb in a multiuser “small-enterprise” type setups.

Also, I have noticed that hsqldb locks everything when it is data is being backed up. Is there a way to avoid that and atleast let reads happen even when the database is being backed up ?

Thanks,

Amit