The Quota.log file can be downloaded from the GUI in STATUS -> Hardware -> Function: Logs.
Did you try to stop and restrat the Apache from the Console screen by entering CTRL ALT T then select "addons" then select Apache then stop and restart?
You can also submit a support ticket from your User Portal and send in the log file to our support team for us to review them as well.
Such system behavior could be related to an issue with the storage disk(s) or the RAID controller itself. Try to check the controller health and storage disks health too.