Dell ActiveArchive™ allows the creation and preservation of persistent images of Dell™ PowerVault™ 715N system data volumes. The Dell ActiveArchive software is available for all PowerVault 715N systems. It can be configured by using the NAS Manager.
A persistent image is a point-in-time copy of a disk volume. A persistent image contains an exact copy of the file system at the time the persistent image was created. If you change a file on the active file system after taking a persistent image, the persistent image contains the old version of the file. If an active file gets corrupted or deleted, you can restore the old version by copying the file from the latest persistent image or restoring the entire volume. Also, because the persistent image contains the contents of the file system when the persistent image was taken, you can perform a backup from the persistent image without stopping all I/O to the file servers, thus eliminating the backup window required by other types of backup.
NOTICE: Persistent images are temporary backups of your data that reside on the same volume
as your data. If the volume becomes damaged, you lose your data, including the persistent
image. Therefore, persistent images do not replace regular backups of your volume.
The Dell ActiveArchive software stores changed data in a cache file. A cache file resides on each volume of your system. By default, the persistent image cache file is 20 percent of each volume. You can use the NAS Manager to change the percentage of the volume that is dedicated to the cache file.
NOTE: You cannot take a persistent image of the operating system volumes or the
recovery operating system drives (C or D).
The Dell ActiveArchive software has two thresholds that provide warnings when the cache file is approaching maximum capacity. The warning threshold logs an event in the event log and displays a warning in the NAS Manager status indicator when the cache file reaches the threshold (default is 80 percent full). The deletion threshold, which is labeled "Begin deleting images" in the NAS Manager, specifies the threshold at which the PowerVault NAS Manager deletes the oldest persistent images with the lowest retention weights until the cache file is below the deletion threshold (default is 90 percent full). The NAS Manager indicates when it deletes persistent images to get below the threshold by displaying an error on the NAS Manager Status page.
When the cache file reaches the deletion threshold, the system starts deleting files, depending on the retention weight and age of the persistent image. The system first looks for the persistent image with the lowest retention weight in the cache file. It then deletes the oldest persistent image with the lowest retention weight until the cache file is below the deletion threshold. After all persistent images with the lowest retention weight have been deleted, Dell ActiveArchive looks for and deletes the oldest files with the next lowest retention weight.
When using persistent images, system performance might be degraded, depending on the rate your data is changing and the number of persistent images kept for each virtual disk. Read performance of the virtual disk remains constant, regardless of the presence of persistent images. Read performance of the persistent image is identical to that of the virtual disk. Write performance, however, might vary. Each initial write to a virtual disk area causes the Dell ActiveArchive software to rewrite the data to the persistent image cache file, and the initial write is slower if the data is being protected by a persistent image. Changes to data that is not protected by a persistent image does not cause a performance degradation.
You can configure the NAS system to store a maximum of 250 persistent images per volume; however, if you exceed the maximum, the oldest persistent image with the lowest retention weight is overwritten. This number of persistent images allows you to schedule multiple persistent images. (You should tailor your schedule depending on how the data is changing.) For example, you could implement a schedule similar to the following schedule:
Seven daily persistent images with a high priority
Two weekly persistent images with a medium priority
Two monthly persistent images with a low priority
This type of schedule gives you good snapshot coverage and ensures that your most recent data has the highest priority.
NOTE: Before changing the image directory name, you must delete all existing persistent
images.
Maximum persistent images — Specifies the maximum number of active persistent images per volume, up to a maximum of 250. When the volume has 250 persistent images stored, starting another persistent image overwrites the oldest persistent image with the lowest retention weight.
Inactive period — Prior to starting a persistent image, the system waits for a period of relative inactivity on the volume being imaged. The default value for this period, which is 5 seconds, allows systems to start an image with a consistent file set and a minimal time-out. Experienced administrators may reduce or increase this value for system optimization. Reducing the inactive period allows persistent images to begin on systems where disk inactivity is rare, at the possible expense of synchronization problems within applications that are concurrently writing to multiple files.
Inactive time-out — Specifies the amount of time the server continues to retry to create a persistent image (default time is 15 minutes). A persistent image cannot start until a period of relative inactivity, specified by Inactive period, occurs. If an interval longer than Inactive time-out passes before the persistent image can begin, the persistent image cannot be taken and an error is displayed in the NAS Manager status indicator and logged in the event log.
Image directory — Specifies the directory name that is to be used for the persistent image mount point. Each persistent image appears as a subdirectory in the volume that is being imaged. The entire content of the volume, as it existed when the persistent image was created, appears under this directory.
If you need to re-establish the system defaults, click Restore Defaults.
Use the appropriate menus to configure the following options.
NOTE: Before changing the cache size, you must delete all persistent images on that
volume.
Warning threshold reached when — Defines the percentage of cache space used that triggers warning messages to the system event log.
Begin deleting images when — Defines the percentage of cache space used that triggers automatic deletion of the oldest persistent images with the lowest retention weight on the system. Automatic persistent image deletions are recorded in the system log.
Cache size — Specifies the percentage of the volume that is allocated to the cache file. Increasing this value allows more and larger persistent images to be maintained. Ensure that adequate space is available on the persistent image files' location drive.
If you need to re-establish the system defaults, click Restore Defaults.
In addition to scheduling persistent images, you can take new persistent images on demand, delete existing persistent images, configure the persistent image environment, and set persistent image retention weights.
In the Tasks list on the Persistent Images page, click New.
In the menu that is displayed, select the Volume(s) to preserve.
Consider the following when selecting the volume(s):
You can take persistent images only of volumes with drive letters, not volumes mounted to a directory (mount points).
If volumes are not protected by RAID 1 or 5 or if volumes are frequently being added and removed, Dell recommends that you make persistent images of individual volumes. Because multivolume persistent images are linked to each other, a multivolume persistent image may become inaccessible if one volume in the multivolume persistent image fails or is removed from the system.
NOTE: To select multiple volumes, press and hold <Ctrl> and select all volumes that are
to be included in the persistent image.
Select the Read Only or Read/Write attribute.
Select the retention weight for the persistent image.
Confirm the persistent image name.
You can use patterns in the persistent image name to differentiate your persistent images. For example if you use a pattern of Snapshot.%i and you take two persistent images, you have Snapshot.1 and Snapshot.2. The default persistent image name pattern is Snapshot %M-%D-%Y %H.%m.%s. Valid pattern macros are as follows:
To change the read only or read/write attribute or the retention weight (deletion priority) of an image, you must edit the persistent image properties by selecting an image from the Persistent Image list, and then clicking Properties in the Tasks list.
To edit the persistent image properties, perform the following steps:
When you click Disks® ActiveArchive® Schedules, the Scheduled Persistent Image page displays a list of all scheduled persistent images and associated tasks. Each scheduled persistent image is identified by the scheduled time, day, frequency, starting date, and target volume ID. Persistent images are identified by time and date and are located in the ActiveArchive directory. The ActiveArchive directory is located in the root of each ActiveArchive volume. Only the administrator can access the ActiveArchive directory. The files and folders in the persistent image directories have the same permissions as the files and folders on the original volume. Persistent image directories are used exactly the same way as conventional system volumes. Unlike conventional volumes, read-only persistent image images are static, recording the precise content of the originating volume at the time you created the persistent image.
The Persistent Images page displays all current active persistent images. Each entry identifies the date and time that the persistent image was created and the volume it preserves. Select an individual persistent image by clicking the radio button to the left of the description.
In the Tasks list on the Persistent Image Schedules page, click New.
Use the menus to select the start time (Start at), the frequency at which to repeat the
persistent image (Repeat every), the day to begin (Begin), the volume(s) to include,
the image attributes (Read-only or Read/Write), the retention weight, number of
images to save (per schedule), and the persistent image name.
NOTE: To select multiple volumes, press and hold <Ctrl> and select all volumes that are
to be included in the persistent image.
NOTE: If volumes are not protected by RAID 1 or 5 or if volumes are frequently being
added and removed, Dell recommends that you make persistent images of individual
volumes. Because multivolume persistent images are linked to each other, a multivolume
persistent image may become inaccessible if one volume in the multivolume persistent
image fails or is removed from the system.
You can use patterns in the persistent image name to differentiate your persistent images. For example if you use a pattern of Snapshot.%i and you take two persistent images, you have Snapshot.1 and Snapshot.2. The default persistent image name pattern is Snapshot %M-%D-%Y %H.%m.%s. Valid pattern macros are as follows:
%M = Month
%D = Day
%Y = Year
%h = Hours in 12-hour format
%H = Hours in 24-hour format
%m = Minute
%s = Second
%i = Instance, which increments once per instance
%a = AM/PM
%W = Day of the week
%w = Three-letter day of the week
%% = Percent sign
Click OK to save the new scheduled persistent image.
In the Tasks list on the Persistent Image Schedules page, click Properties.
Use the appropriate menus to select the starting time, the frequency at which to
repeat the persistent image (Repeat every frequency), the day to begin, the volume(s),
the image attributes (Read-only or Read/Write), and the number of images to save
(per schedule).
NOTE: To select multiple volumes, press and hold <Ctrl> and select all volumes that are
to be included in the persistent image.
NOTE: If volumes are not protected by RAID 1 or 5 or if volumes are frequently being
added and removed, Dell recommends that you make persistent images of individual
volumes. Because multivolume persistent images are linked to each other, a multivolume
persistent image may become inaccessible if one volume in the multivolume persistent
image fails or is removed from the system.
Click OK to modify the schedule or Cancel to leave the schedule intact.
NOTE: Only Windows clients (CIFS) can access Dell ActiveArchive persistent images.
NOTE: The name of the utility that creates persistent images is Dell ActiveArchive.
The name of the directory where Dell ActiveArchive persistent images are stored is
ActiveArchive.
By default, administrators can access the ActiveArchive directory in the root of each volume. Each persistent image is displayed separately with a date and time stamp showing when the persistent image occurred. The administrator can browse the persistent image as if it were a standard volume. Each persistent image is mounted as a volume on the file system to allow access by clients. Persistent images are created as read-only or write-only.
Persistent image directories are used in the same way that conventional directories are used. The files and folders in the persistent image directories have the same permissions as the files and folders on the original volume. All persistent images are persistent and survive system power losses or reboots.
The files and folders within a persistent image are identical to the permissions on the original files and folders. However, by default, the ActiveArchive directory is restricted to administrator access only. To allow users to access the persistent images, the system administrator must modify the permissions for the ActiveArchive directory.
Use the PowerVault NAS Manager to change the ActiveArchive directory permissions by performing the following steps:
In the Tasks list on the Shared Folders page, click New.
Type the share name ActiveArchives and path
volume_letter:\ActiveArchives, where volume_letter is the volume of the
persistent images.
NOTE: Ignore the Comment field for NFS, FTP, and HTTP shares.
Check the Microsoft Windows (CIFS) box.
Click CIFS Sharing and add the users that you want to have access to persistent
images.
Click OK.
Users can access persistent images from a Windows 2000 client by performing the following steps:
Right-click My Appliance, and select Map Network Drive.
Map to the ActiveArchives directory as a user that has permissions to the
ActiveArchives share.
For Folder, type \\Dellxxxxxxx\ActiveArchives, where Dellxxxxxxx is the
name of the NAS system.
The default system name is Dellxxxxxxx, where xxxxxxx is the system's service tag number. For example, if your service tag number is 1234567, enter DELL1234567. You can find the service tag number on the top cover of your NAS system.
Use Windows Explorer to navigate to the ActiveArchive directory on the newly
mapped drive.
Windows Explorer has a limitation of 255 characters in a filename, including the path. When you make a persistent image, the entire path and filename are stored in addition to the Dell ActiveArchives default path and persistent image name. The default Dell ActiveArchives naming convention would result in a name such as the following:
The original path and filename and the Dell ActiveArchives default path might exceed the 255-character limit and become inaccessible through Windows Explorer.
If a file becomes inaccessible because of the 255-character limit, perform the following steps to ensure that you can access long path and file names in Windows Explorer:
Create a share for the desired snapshot folder. For example:
E:\ActiveArchives\Snapshot 01-01-2001 12.00.00\
Access that share through the desired client.
The path and filename no longer include the additional directory information, which shortens the path and filename to the original character length. You can now access the file through Windows Explorer.
To restore a volume(s) from a persistent image, you must select the persistent image to be restored. Ensure that you select the persistent image carefully because any activity that occurred after the persistent image was taken is lost.
NOTICE: Restoring a volume restores the volume back to the state of the volume at the time
the persistent image was made. This restore destroys all data on the volume and replaces it with
the data from the persistent image.
NOTICE: A volume is dismounted during a restore. All reads and writes to a volume that occur
during the restore process are denied. Therefore, you must stop all I/O traffic to a volume while
restoring it.
To restore volumes from a persistent image, perform the following steps:
Click the persistent image that is to be restored.
Click Restore.
Click OK to restore the volumes protected by the persistent image, or click Cancel to
leave the volume intact.
NOTE: Restoring persistent images that contain multiple volumes restores all of the
volumes in the persistent image. If you want the ability to restore a single volume, you
must take single volume persistent images.
NOTE: If you delete a share from a volume after a snapshot is taken, that share will
not be accessible after you restore the snapshot. For example, if you create a
persistent image of volume E, which has a share called "users," and you later delete
"users," when you restore volume E, the "users" share will not be accessible, although
the directory will still exist and contain the files.
Applying a selected language changes the graphical user interface to that language, but it does not change the language in which the Dell ActiveArchive event log messages are generated. The messages are generated in English unless you run a batch file to change the language to one of the following supported languages:
English
French
German
Japanese
Spanish
To change the language in which the event log messages are generated, perform the following steps:
NOTICE: Defragmenting a volume containing persistent images without using the following
procedure can corrupt your persistent images and degrade your system performance.
NOTE: If you do not have persistent images on your volume, this procedure does not
apply.
NOTE: To defragment a volume, you must delete all persistent images on that volume.
To defragment a volume containing persistent images, perform the following steps:
