Preparing to install SnapManager

Assessing volume size

SnapDrive storage requirements

In addition to the space required for your virtual disks, SnapDrive requires space to store data that has changed between snapshots and the active file system of the virtual disk. It also requires space to store metadata. Allowing for this additional space ensures that taking multiple snapshots does not encroach on the virtual disk files in the volume.

When you create filer volumes to hold virtual disks, you must take into account the following SnapDrive requirements:

To create snapshots, the volume storing the virtual disk must be at least twice the size of that virtual disk.
By extension, a filer volume must have at least twice the capacity of all the virtual disks it contains.
The volume must have enough free space for the number of snapshots you intend to keep online.
In sizing volumes, take into account how many day's worth of snapshots will be online at the same time.

The first snapshot lock uses disk space equal to the virtual disk file size itself (thus, double the requirement). Additional snapshots add to this.

Virtual disk size calculations for the Data directory

To ensure that you create volumes to meet these SnapDrive requirements, you must calculate the potential size of your virtual disks. The following formula works best to calculate Domino Data directory size for a Domino mail server:

Data directory size = (mail files* mailbox quota)* 2 + deleted item 
cache + NAB (Name and Address Book)

Example

Given these requirements, the following parameters can be expressed by the formula shown after them:

1,000 users with 100 MB quotas for mail files
Double the space for the first snapshot
The deleted item cache is 10%

(((1000*100 MB)*2)*1.10)= about 220 GB + NAB

SnapManager storage requirements for transaction logs

SnapManager Backup backs up transaction logs that were not committed to the Domino Data directory at the time of the backup. It also saves copies of the transaction logs committed to the Data directory to be purged from the active file system during the backup. The number of logs that accumulates between backups vary from server to server, but is dependent on the amount of transactions and E-mails sent and received. Each Domino transaction log consumes 64 MB of space.

Estimating the amount of space required for transaction logs

You can determine how much disk space is required for your Domino Data directory transaction logs by first estimating the number of transaction logs that are generated on your server.

To estimate how many transaction logs are generated, note the number of transaction logs that accumulate in the transaction log directory immediately before a backup. Use that number to estimate how much disk space you need. (You should do this over a period of several days and use the maximum number).

The following formula works best for calculating virtual disk size required for a transaction log drive:

virtual disk size = ((number of transaction logs generated per day 
* 64 MB) * ( number of snapshots to keep online + 1 for the active 
file system))

Example:

Given the following parameters, at least 6 GB of virtual disk drive is required to accommodate the transaction logs for the example Domino databases. This is expressed by the formula following the parameters:

The server generates 5 transaction logs in one day.
Each transaction log is 64 MB.
There is about 1 GB of transaction logs at the end of the day.
The plan is to keep five days' of SnapManager backups online at the same time.

((5 * 64 MB)*(5+1))=1920 MB or about 1.2 GB