The disk quota is the maximum amount of data you're allowed to store in a given disk or location. You should first verify if you're making proper use of your disk space (i.e., do you have thousands of temporary files you no longer need but failed to remove?). If you actually decide you simply need more space, you should contact your hosting provider and upgrade your plan.
In your case, you might consider not using the system-wide temporary directory for session storage.
与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…
