Can we store files and attachments in external storage from SFDC. We are storing our file on NAS(network storage). Since size of files is very big , so we store file on NAS and keep the storage link in sfdc.Please let me know how can we achieve this.
Although it's not cheap or inexpensive, this might be an appropriate situation to consider implementing Lightning Connect which would use ODATA to connect with your NAS database that's external to Salesforce. Lightning Connect now has Read/Write capabilities and integrates very well with Salesforce. You'd get the benefits of the less expensive storage on your NAS yet still have seamless integration with Salesforce that would be transparent to your community users.
I'm in no way suggesting this is the only solution, instead that this is an option you may want to consider.