all of my server has 27.1 gigs space totally.but
r1soft shows 38 gigs.
I asked about this issue from my datacenter they said:this is normal behavior since you have
incremental backups meaning that on monday it will do a full 27gig backup of your system and the rest of the week it will backup only the data that changed that day and adds it to the previous backup of 27gig So at the end of the week you will end up with a bigger backup then 27gig It's perfectl normal
Incremental backups will have an impact on the amount of data that is actually stored on your R1Soft backup.
There is also a slight increase in the amount of data that is stored due to Filesystem Overhead.
I don't really know how to explain the phenomenon of filesystem overhead in a simple way, however.
Without going too in-depth in the details, the FS overhead is the disk space used by the operating system to store data relevant to inodes. The amount of overhead will vary depending on several factors such as the size of the hard drive.
R1Soft CDP uses a virtual full backup process. You take an initial replica which is all of the allocated blocks in your file system. From then on it uses an asynchronous-replication process to copy only changed blocks at the frequency of your schedule.
You define... keep X recovery points (backups). For each recovery point only the deltas (block level differences) between each recovery point are stored.
If a disk block does not change it is only ever stored once. So...
1) To keep different versions (recovery points) of your file system CR1Soft needs to store the block level differences that make up that point-in-time version of your disk (not sure how many you are keeping).
2) There is some overhead in storing these recovery points... for example we have to be able to locate and index these block level deltas to create a virtual full backup.
3) You can enable compression to reduce the size of the deltas stored.
How is this different from typical incremental or full backup?
* A delta (block) is only store once no matter how many backups you keep (we call these recovery points).
* The asynchronous replication process knows what the deltas are and only reads those form disk. This means (after the first initial replica or seed) it only takes minutes to create a full backup.
For example its not uncommon to complete a backup that is virtually a full backup in as little as 5 or 10 minutes!