Specifications

Lotus Redbooks Wiki – IBM Lotus Notes and Domino V8.5 Deployment Guide
160
DAOS
Domino Attachment and Object Service (DAOS) is a large object store for Domino where its content is
outside of the Notes database. The common content is stored only once, meaning that it consolidates the
storage of multiple attachments for all the users hosted on a particular Domino server. On the shared
content, DAOS manages reference counts. Since DAOS is a server-based feature, the access to its objects
is totally transparent to the Domino server tasks (HTTP, Replication, FT Indexing) and applications (C-API
calls, Agents, LotusScript).
A DAOS object is called a Notes Large Object (NLO). For each attachment processed by DAOS, an NLO file
is created in the DAOS store, that is a simple folder at the operating system level. Each NLO file is created
based on the checksum of the content of the attachment represented. Using this checksum process, DAOS
can determine if the attachment is the same or different than an existing one. For security purposes, each
NLO is encrypted by default with the server's key to protect it.
Planning
Now that we know what DAOS is, what steps should be taken in the planning for its deployment?
First, we need to determine where we will put the DAOS store. The DAOS store is one folder at the
operating system level, under which all the NLO files are stored.
We need also to plan for the minimum size of the attachments that will be put into the DAOS store. If we
choose a size too small, the DAOS server will create lots of NLO files, thus using more disk space than
really needed. On the other hand, if we choose a size too large, we lose the potential the savings that DAOS
was designed to provide.
Another thing we need to determine is how long we hold on to DAOS objects once the last reference is
deleted. One key consideration is the frequency of database restores. An important thing to understand is
that databases and NLO files are backed up independently, meaning that you have to change your Domino
backup jobs to include the DAOS store, just like any other folder. When you restore a database, you have to
make sure that all the necessary NLO files are present, or, if not, restored from backup as well. Finding the
right balance will save lots of time and effort when restoring databases. Once the last reference is deleted, if
you purge the NLO files too soon, you'll have to restore them when you restore a database, requiring more
operational administration. If you keep them too long, you're losing valuable disk space and might have to
add extra disks for growth, which reduce the disk space savings.
The last thing to plan is security for the DAOS repository. Should it be encrypted or not? This depends on
how secure the Domino server is. By default, NLO files are encrypted using the server key.
This means that you cannot copy a .nlo file to another DAOS directory for another server. It won’t work.
Encryption can be turned off by using the variable “DAOS_ENCRYPT_NLO=0” in the server's Notes.ini file.
DAOS Estimator
The DAOS Estimator tool will assist in the DAOS planning phase. This tool examines a set of Notes
databases and provides a summary with the following information:
• Total size of NSFs examined
• Total attachments found
• Total duplicate attachments found
• Total DAOS eligible attachments
• Estimate size of DAOS store (folder)
• Total disk savings