In the hardware compatibility document it states for MCS-7835-H2 supported but with this remark:
(2) Supported, but note that Cisco Unified Communications Manager 5.0 and later require minimum memory and disk size as described in the table below. For Cisco Unified Communications Manager 8.0(3) and above, it is strongly recommended to upgrade to minimum 4GB RAM and 146GB disk drive; whether this is necessary for your deployment is design-dependent and depends on call volume, installed locales, dial plans, phone firmware loads, music files, etc. See technical documentation for guidance. Use http://www.cisco.com/go/swonly to get supported memory and disk part numbers.
MCS 7835
memory: 2 GB for -H2, -I2 and older. For version 8.0(3) or higher, 4 GB strongly recommended.
HD: 72 GB for -H2, -I2 and older. For version 8.0(3) or higher, 146 GB strongly recommended.
Likely the release after 8.5 (if not 8.5 as well) will enforce the usage of these parameters. So provided these server models would still be supported at that time, you may wan to consider replacing this now.
This used to be the cisco part number: HDD-7835-H2-146= However this appears to be end of sale this is the migration option we offer:
Customers may be able to continue to purchase the Cisco 7800 Series Media Convergence Server Spare Parts through the Cisco Certified Refurbished Equipment program. Refurbished units may be available in limited supply for sale in certain countries on a first-come, first-served basis until the Last Date of Support has been reached. For information about the Cisco Certified Refurbished Equipment program, go to: http://www.cisco.com/go/eos.
If you require further info about acquiring hard disk or memory I would suggest you to address that with your account team.
So as the documentation states you can also run with 2GB memory and 72GB hard drive. It is specifically in case you have many locales, tftp custom files, ... that you could potentially run into problems. Or you can choose to migrate to different hardware as well.
