what is soft quota and hard quota.

The hard quota is the amount of disk usage that the user may not exceed at any time.
The soft quota is a lower limit, which the user is allowed to breach for up to a time period.
1. Hard quotas prevent users from writing data to disk. With hard quotas, the utility automatically limits the user's disk space for you, and no users are granted exceptions. Once users are about to reach their quota, they come to you for help.
2. Soft quotas send you alerts when users are about to exceed disk space. Unlike hard quotas, there is no physical restriction to prevent users from saving their data. However, you do get alerts and can create a corporate policy to help manage data.