Albert Buendia  Junio 30 2010
Albert Buendia  Junio 30 2010

What is DAOS?
The IBM Lotus Domino Attachment and Object Service (DAOS) allows you to save a significant amount of space at the file level, minimizes I/O and gives you more flexibility with your file storage options; reducing your total cost of ownership and helping employ green computing practices. Lotus Domino no longer needs to save a separate and complete copy of every document attachment. Instead, the DAOS-enabled server saves one copy of each unique attachment in an internal repository, and then refers to the same file from multiple documents in one or more databases on the same server. When an attached file is large and a message containing it is broadcast to thousands of users, creating a separate copy of the message for each recipient could require several gigabytes of disk space. Multiple copies of the same attachment are often also proliferated in mail threads with multiple replies. With DAOS enabled, disk space usage is substantially reduced.

A DAOS object is called a Notes Large Object (NLO). For each unique attachment processed by DAOS, an NLO file is created in the DAOS repository. 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 ones already in the repository. For security purposes, each NLO is encrypted by default with the server's key to protect it.

Don't have a lot of duplicate attachment data? DAOS offers more than just overall disk space savings. By removing attachment data from the NSF, it can be treated differently. Attachment data is static, and typically has much lower traffic rates than the data directory. DAOS provides the flexibility to choose cheaper storage options to free up the prime disk real estate on your server. The static nature of NLO files makes them a perfect candidate for big savings using incremental backup techniques.

Still want more? An improvement introduced in version 8.5.1 reduces network traffic by not transmitting attachments to a DAOS-enabled server that already has the attachment in its DAOS repository. As long as the 8.5.1 destination server has DAOS, and the attachment is in the repository, any 8.5.1 source whether DAOS-enabled or not, server or Notes client, will not have to send the attachment contents. And if that still isn't enough, there are even more DAOS features and enhancements coming up in 8.5.2.

DAOS is...
  • a new feature that was introduced in the IBM Lotus Domino Server version 8.5.0
  • supported on all platforms
  • transparent to clients. Whether you use a current or older Notes client, a BlackBerry device, Lotus Traveler, etc., it will receive the attachment data in the same way
  • not just for mail attachments. It doesn't matter what type of application you have
  • not limited to disk storage savings

For more information, refer to the devWorks article, IBM Lotus Domino going green: The new Lotus Domino attachment and object service
Helpful Wiki, devWorks and InfoCenter articles:

- Attachment consolidation

- Marking a database for attachment consolidation

- Specifying server settings for attachment consolidation


- DAOS Quick Start guide

- DAOS best practices

- DAOS backup and restore

- Demystifying the Domino console commands for DAOS

- DAOS: How to set up a regularly scheduled resynchronization

- Achieving ultimate storage and server cost savings with DAOS in IBM Lotus Notes and Lotus Domino 8.5

- DAOS Troubleshooting

- Is Shared Mail supported in Notes and Domino 8.5? (Technote 1328028)

- Transaction Logging Best Practices (Technote 7009309)

- New DAOS features in Notes/Domino 8.5.1 (Technote 1411307)

- How can I move the location of the DAOS subdirectory (Technote 1415153)

- Transient attachments and DAOS (Technote 1426551)

- How can the actual disk savings from DAOS be computed? (Technote 1418283)

- Is there a way to select "DAOS" when running compact from the Domino Administrator client? (Technote 1413681)

- Download the Domino Attachment and Object Service Estimator Tool version 1.5 (Technote 4021920)

- Installation instructions for the DAOS Estimator Tool for System i (OS/400) (Technote 7015216)

Recent Open Mic Discussion
We recently conducted an Open Mic conference call on DAOS. Here are a few of the questions asked by customers and answered by Lotus Development and Support during that call. The full list of questions and answers from that session will be posted to Technote 1432989 in a couple of weeks. For a schedule of upcoming Open Mic sessions, please see the Lotus Support Technical Exchange Events page or the 2010 Open Mic Q&A sessions wiki article.

Q: What version of the product is recommended?
A: For a production environment, we recommend that you deploy DAOS with at least version 8.5.1 FP2 IF1, or 8.5.1 FP3.

Q: Does DAOS needs its own independent server?
A: No. DAOS can be enabled on each Domino server to take advantage of its benefits.

Q: Is there any detection and notification if a compact needs to be run to reprocess messages for attachments?
A: Once DAOS is enabled on an NSF, all subsequently written attachments will be considered for DAOS participation automatically.

Q: Can we enable DAOS on databases ODS 43 (Domino 7 ODS)?
A: No. ODS 51 (new to 8.5) is required. You can upgrade via create_r85_databases=1 INI parameter and running copy-style compaction.

Q: Do all databases on the server need to be at ODS 51 or only the ones that are DAOS-enabled?
A: Only databases participating in DAOS storage need to be at ODS 51.

Q: Any issues with a Notes 7 client accessing application databases that are DAOS-enabled on a Domino 8.5.1 server?
A: No, attachment access is transparent to the client.

Q: Is copy-style compaction recommended for all databases, not only the mail file?
A: Yes, a copy-style compaction is necessary to DAOS-enable existing attachments for all database types.

Q: If you send an email to another Lotus server in the same domain with DAOS enabled on both, is the attachment saved in both DAOS stores on each server?
A: Currently, DAOS does not share NLOs across servers, so if both servers are DAOS-enabled, then the attachment will be stored on both servers.

Q: Is each NLO file encrypted as an attachment?
A: By default, all NLO files are encrypted with the server key. There is a notes.ini variable that you can set to disable the NLO encryption. This encryption is in addition to any other compression/encryption options that you had set at the NSF level.

Q: How or when are the attachments cleaned up? What are the options for removing the attachments permanently?
A: Every morning at 2am, a DAOS prune process runs to remove NLOs with zero references after the deferred delete interval has passed.

Q: Are there any size limitations for attachments in DAOS (other than operating system limitations)?
A: There are no size limits on attachments.

Q: What is the purpose of the DAOS catalog file? Is there any essential information in that file that can be lost or that is not stored in the NLO files?
A: The catalog file tracks all NLO objects and databases that participate in DAOS storage.

Q: Can I expect any issues with an upgrade/move from Domino on Windows 32-bit to Windows 64-bit?
A: DAOS should not be affected by this upgrade.

Q: If we have mail databases, Document library, and Discussion databases on the same server, will DAOS remove the attachments on all databases?
A: DAOS is enabled per database; however, you can run a copy-style compaction against a directory to enable all databases in the specified directory.

Q: With transaction logging required for DAOS, what is the recommended logging style for DAOS?
A: It depends on what your requirements are, but either circular or archive are supported and work.

Q: Why is transaction logging required for DAOS?
A: It is required because of the need to keep database actions and object actions within the same transaction.

Q: Is there anything to watch out for implementing DAOS on the iSeries?
A: iSeries seems to be more sensitive to a (potentially) large number of NLO files. For that reason, the default minimum participation size is set higher (1MB) for iSeries than the other platforms to reduce the number of NLO files created. Also, due to the architecture of the iSeries disk subsystem, the physical location of the DAOS repository and transaction logs is less critical. We recommend for all platforms that the DAOS repository be not logically located underneath the data directory, as some utilities may traverse the repository unnecessarily while scanning the data directory.
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