Some Data Domain Maximums !

Maximum Number of Supported Inodes#

An NFS or CIFS client request causes a Data Domain system to report a capacity of about two billion inodes (files and directories). A Data Domain system can exceed that number, but the reporting on the client may be incorrect.

Maximum Path Name Length#
The maximum length of a full path name (including the characters in /data/col1/backup) is 1023 bytes. The maximum length of a symbolic link is also 1023 bytes.

Max Support Bundles#
The system supports a maximum of 10 support bundles. If you attempt to generate an 11th support bundle, DD System Manager displays a warning that prompts you to click OK or Cancel. If you click OK to continue, the oldest support bundle, which is listed in the warning message, is deleted.

Maximum Days Between Change#
The maximum number of days between password changes that you allow a user. Default is 99999.

Managing HTTP and HTTPS Access(System ports and session timeout values)#
In the Session Timeout text entry box, enter the interval in seconds that must elapse before connection closes. The minimum is 60 seconds and the maximum is 31536000 seconds (one year).

Virtual Interfaces#
The virtual-name must be in the form vethx where x is a number. The recommended maximum number is 99 because of name size limitations.

MTU Size#
Although 9000 is the maximum size, to be backwardly compatible, the DD OS accepts up to 9014, but sets the size to 9000 when it is greater than 9000 and less than or equal to 9014.

Upgrade Packages#
A maximum of 5 upgrade packages can be uploaded using DD System Manager. To continue with this procedure, remove the excess images (see Removing an Upgrade.

This table recommends the maximum number of systems and user sessions that can be managed by DD System Manager#

Maximum Initiators#
An access group may contain multiple initiators (a maximum of 128), but an initiator can exist in only one access group. A maximum of 512 initiators can be configured for a Data Domain system.

Maximum Groups#

When you create or configure an access group on a Data Domain system, each Data Domain system device (media changer or drive) can be assigned to multiple groups. Devices assigned to other groups, however, cannot be assigned to TapeServer. A maximum of 128 groups can be created.

Maximum LUNs #

The maximum LUN accepted when creating an access group is 16383. A LUN can be used only once for an individual group. The same LUN can be used

with multiple groups.

Maximum Libraries#
VTL supports a maximum of 64 libraries per system (that is, 64 concurrently active virtual tape library instances on each Data Domain system).

CAPs Maximum#
CAPs (cartridge access ports) – VTL supports a maximum of:
-100 CAPs per library
-1000 CAPs per system

Slots Maximum:
Slots – VTL supports a maximum of:
– 32,000 slots per library
– 64,000 slots per system

I/O Maximum#
The maximum supported I/O size for any Data Domain system using the VTL is 1 MB.

Maximum Snapshots#
The maximum number of snapshots allowed per MTree is 750. Warnings are sent when the number of snapshots per MTree reaches 90% of the maximum allowed number (from 675 to 749 snapshots), and an alert is generated when the maximum number is reached.To clear the warning, expire snapshots and then run the file system cleaning operation.


  • Number of Streams Supported:
    Each optimized synthetic backup  accounts for two streams:
    one write and one read stream. Therefore, the maximum number of concurrent streams for the synthetic backup cannot exceed half of the total streams supported for the Data Domain system. 
  • Retention Period: Specifying a minimum retention period of less than 12 hours, or a maximum retention period longer than 70 years, results in an error.
  • Quota: MTree quotas apply to ingest operations. These quotas can be applied to data on systems that have the DD Extended Retention software, regardless of which tier it resides on; as well as VTL, DD Boost, CIFS, and NFS.
    Snapshots are not counted. Quota cannot be set on the /data/col1/backup directory.
    The maximum quota value allowed is 4096 PiB.
  • Data Domain Supports up to 180 source appliances to one target device.
  • Each Data Domain system model supports a maximum number of simultaneous connections. To NetWorker this translates to the number of streams as part of the parallelism settings. Do not exceed server parallelism for the allowable Data Domain model’s max streams. If this number is exceeded, performance degradation can occur.
  • Use the net show hardware command to see how many interfaces are configured and at what speed they are connected
    # net show hardware
    Port   Speed      Duplex    Supp Speeds   Hardware Address    Physical   Link Status
    —-   ——–   ——-   ———–   —————–   ——–   ———–
    eth0   1000Mb/s   full      10/100/1000   00:23:8b:57:77:5f   Copper     yes
    eth1   1000Mb/s   full      10/100/1000   00:23:8b:57:77:60   Copper     yes
    —-   ——–   ——-   ———–   —————–   ——–   ———–
    In the above example both the interfaces eth0 and eth1 are connected (Link Status “yes”), the speed of each is 1000 mega-bits per second and the duplex setting is full. In this example, the maximum throughput for any single interface is 125 mega-bytes per second; and the theoretical maximum transfer speed for this data domain system is 250 mega-bytes per second in each direction.
    From <https://emc–>



  • Memory considerations:

The Target sessions attribute refers to the optimal number of backup sessions accepted by any active NetWorker device. If a device has a Target session setting of 4, NetWorker will look for another available device when, say, a fifth stream is started.

If no device is available the target sessions setting will be ignored and the extra stream will get added to the initial four on the original device. The Max session setting determines the absolute maximum number of streams a device will allow. The Max session is a hard limit and the Target session a soft limit. The default setting for

the Data Domain device Target session is 1 and the Default Max session is set to 4, with an overall hard limit of 10.

Each read-write device (active nsrmmd process) that takes one save stream requires 48 MB of RAM on the storage node. Each additional save stream requires 16 MB. The corresponding read-only device requires 16 MB, regardless of the number of save streams. Thus one save stream requires 64 MB, four save streams require 128 MB,and the maximum of 10 save streams requires 224 MB.

 It is recommended that no more than 16 Data Domain device types reside on a storage node that is running the maximum number of 10 save streams per device.

This scenario would require (16 x 224) = 3.6 GB of physical memory on the storage node.
 It is recommended that a storage node have at least 8 GB of RAM when hosting NetWorker Data Domain devices. The use of two interface connections (1 GbE or 10 GbE) is also highly recommended.

To determine the amount of memory needed for your particular deployment, use the following formula as a guideline:

m=n ((16*s)+64)

Where m= Memory requirements in MB, n= Number of DD devices, s= Max sessions


About Ahmad Sabry ElGendi
This entry was posted in E20-385, EMC. Bookmark the permalink.

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