Netmail Detach helps organizations minimize the size of their mail system by removing attachments from their messages and storing them only once in Netmail Store, through single instance storage (SIS). Stripped attachments are then replaced by HTTP links that point to the attachments in Netmail Store. If an organization already has a storage system in place (e.g., SAN or NAS), it is possible to configure Netmail Store Emulator. The Netmail Store Emulator behaves like Netmail Store but runs on the file system. It gives Netmail HTTP access to your SAN, allowing it to fetch attachments from your storage system, when required.
Netmail can remove attachments at three points:
- At the gateway (for incoming messages from the Internet)
- From messages already in the Exchange mail server
- From new messages being sent internally (before they ever reach the Exchange server)
When messages are forwarded internally within the organization, attachments are not re-attached to their respective messages. Recipients need only to click the HTTP links to access their attachments. This applies regardless of whether the original messages came directly from outside the organization or were stripped of their attachments from within the Exchange system.
For outbound messages (sent to external recipients), attachments are re-attached at the gateway before the messages are sent out. It is possible to forgo the re-attachment at the gateway for external recipients, but doing so requires opening the access to Netmail Store to the Internet. While it is safe, most organizations choose to re-attach the files.
Note: Attachment removal at the gateway is applicable to both GroupWise and Exchange environments. However, attachment removal from within the mail system applies only to Exchange environments, as GroupWise still provides SIS for attachments.
Netmail Detach System Requirements
Netmail Detach makes use of Netmail Archive, Netmail Secure, and Netmail Store. They can be deployed together or as separate pieces, depending on your organization's needs and email environment. As such, ensure that your system meets the requirements needed for each of the components your organization is using.
|Archive Server (Master or Worker Nodes)|
The Archive Server is responsible for connecting to the back-end mail server (GroupWise or Exchange), ingesting data, converting it to XML, and storing the data.
Operating System (pre-installed on VM):
Software (pre-installed on VM):
Each Netmail Secure node that is deployed must be allocated the resources below.
Software (pre-installed on VM):
|Minimum Requirements for Netmail Store|
Netmail Store installs and runs on enterprise-class x86 commodity hardware. At least three Netmail Store nodes are required in a cluster to ensure adequate resiliency to failures.
Netmail Store nodes are designed to run using lights-out management (or out-of-band management) and do not require a keyboard, monitor, and mouse (KVM) to operate.
The following table lists the minimum (and recommended) hardware requirements for a Netmail Store cluster.
Expand for more detailed information about hardware requirements
Memory Sizing Requirements
Review the following sections for factors that will influence how you size memory and erasure coding, as well as how you configure Netmail Store.
How RAM Affects Storage
The storage cluster is capable of holding the sum of the maximum object counts from all nodes in the cluster. The number of individual objects that can be stored on a Netmail Store node depends both on its drive capacity and the amount of its system RAM.
The following table shows estimates of the maximum possible number of replicated objects (regardless of size) that you can store on a node, based on the amount of RAM in the node, with the default 2 replicas being store. Each replica takes one slot in the in-memory index maintained on the node.
How the Overlay Index Affects RAM
Larger clusters (those above 32 nodes by default) need additional RAM resources to take advantage of the Overlay Index.
To store the same number of
Smaller clusters and larger clusters where the Overlay Index is disabled do not need this additional RAM.
How Erasure Coding Affects RAM
The number of erasure-coded objects that can be stored on a node per GB of RAM is dependent on the size of the object and the configured encoding. The erasure-coding manifest takes two index slots per object, regardless of the type of object (named, unnamed immutable, or unnamed anchor). Each erasure-coded segment in an erasure set takes one index slot. Larger objects can have multiple erasure sets, so you would have multiple sets of segments.
For example, with the default segment size of 200 MB and a configured encoding of
Additional RAM: Larger clusters (above 32 nodes by default) need additional RAM resources to take advantage of the Overlay Index. For erasure-coded objects, allocate 10% additional RAM to enable the Overlay Index.
In summary, Erasure coding users about half the space of replication, but it requires more RAM.
How to Configure for Small Objects
Netmail Store allows you to store objects up to a maximum of 4 TB. However, if you store mostly small files, configure your storage cluster accordingly.
By default, Netmail Store allocates a small amount of disk space to store, write, and delete the disk's file change logs (journals). In typical deployments, this default amount is plenty because the remainder of the disk will be filled by objects before the log space is consumed.
However, for installations writing mostly small objects (1 MB and under), the file log space can fill up before the disk space. If your cluster usage focuses on small objects, be sure to increase the configurable amount of log space allocated on the disk before you boot Netmail Store on the node for the first time.
The parameters used to change this allocation differ depending on the software version in use.
By default, Netmail Store is configured to allocate a small amount of disk space to store write and delete journals.
Supporting High-Performance Clusters
For the demands of high-performance clusters, Netmail Store benefits from fast CPUs and processor technologies, such as large caches, 64-bit computing, and fast Front Side Bus (FSB) architectures.
To design a storage cluster for peak performance, maximize these variables:
Important: If the cluster node CPU supports hyper-threading, be sure to disable this feature within the BIOS setup to prevent single-CPU degradation in Netmail Store.
For best performance, try to balance resources across your nodes as evenly as possible. For example, in a cluster of nodes with 7 GB of RAM, adding several new nodes with 70 GB of RAM could overwhelm those nodes and have a negative impact on the cluster.
Because Netmail Store is highly scalable, creating a large cluster and spreading the user request load across multiple storage nodes significantly improves data throughput, and this improvement increases as you add nodes to the cluster.
Tip: Using multiple replicas when storing objects in the cluster is an excellent way to get the most out of Netmail Store, because each copy provides redundancy and improves performance.
Selecting Hard Drives
Selecting appropriate hard drives for the Netmail Store nodes improves both performance and recovery, in the event of a node or disk failure. When selecting drives, these are the key criteria, which are detailed below:
The critical factor is whether the hard drive is designed for the demands of a cluster. Enterprise-level hard drives are rated for 24x7 continuous-duty cycles and have time-constrained error recovery logic that is suitable for server deployments where error recovery is handled at a higher level than its on-board controller.
In contrast, consumer-level hard drives are rated for desktop use only; they have limited-duty cycles and incorporate error recovery logic that can pause all I/O operations for minutes at a time. These extended error recovery periods and non-continuous duty cycles are not suitable or supported for Netmail Store deployments.
The reliability of hard drives from the same manufacturer will vary, because the drive models target different intended use and duty cycles:
You can optimize the performance and data throughput of the storage sub-system in a node by selecting drives with these characteristics:
Use of independent disk controllers is often driven by the storage bus type in the computer system and hard drives.
Drive Capacity and Recovery
You can improve the failure and recovery characteristics of a node when a drive fails by selecting drives with server-class features yet that are not the highest capacity.
Drive Controller Compatibility
The best practice is to check with Netmail before investing in new equipment, both for initial deployment and for future expansion of your cluster. Netmail can help you avoid problems not only with drive controller options but also with network card choices.
Netmail Store greatly simplifies hardware maintenance by making drives independent of their chassis and their drive slots. As long as your drive controllers are compatible, you are free to move drives as you need.
Netmail Store supports a variety of hardware, and clusters can blend hardware as older equipment fails or is decommissioned and replaced. The largest issue with mixing hardware is incompatibility among the drive controllers.
Track types of drive controllers
When you administer the cluster, monitor your hardware inventory with special attention to the drive controllers. Some RAID controllers, for example, reserve part of the drive for controller-specific information (DDF). Once a volume is formatted for use by Netmail Store, it must be used with a chassis having that specific controller and controller configuration.
To save time and data movement, many maintenance tasks involve physically relocating volumes between chassis. Use the inventory of your drive controller types to easily spot when movement of formatted volumes is prohibited due to drive controller incompatibility.
Disable volume autoformatting
For additional safety in a cluster with incompatible controllers, set this option:
This configuration setting prevents volume reformatting if you accidentally move a volume between incompatible controllers.
With automatic drive formatting disabled, you will need to format your new volumes outside the cluster, which you can do using a spare chassis running Netmail Store with the desired controller.
Test compatibility outside cluster
To determine controller compatibility safely, test outside of your production cluster, do the following:
1. Set up two spare chassis, each with the controller being compared.
2. In the first chassis, format a new volume in Netmail Store.
3. Move the volume to the second chassis and watch the log for error messages during mount or for any attempt to reformat the volume.
4. Retire the volume in the second chassis and move it back to the first.
5. Again, watch for errors or attempts to reformat the volume.
6. If all goes well, erase the drive using
If no problems occur during this test, you can confidently swap volumes between these chassis within your cluster. If this test runs into trouble, do not swap volumes between these controllers.