B Open File Limits And Recommended Streams Per Nas Share For D2D Backup Systems - HP D2D Manual

B Open file limits and recommended streams per NAS share
for D2D Backup Systems
Table 1 Open file limits and recommended streams per share
Max files per share
Max Open files per
share > 24 MB (DD
threshold)
Max Open files per
appliance > 24 MB
(DD threshold)
Max Total Open files
per share
Suggested maximum
concurrent operations
per share
Suggested maximum
concurrent operations
per appliance
Max Nos of files per share is set at 25000 because of replication considerations. To actually store
more data most backup software allows the size of the D2D NAS "Containers" to be increased.
For example, with CommVault the default container size is 2 GB but the user can easily change
this to 16 GB or more.
The HP D2D NAS target for backup does not deduplicate the first 24 MB of any file for performance
reasons. Some backup applications generate control files during backup to NAS that are constantly
changing – to try and deduplicate constantly changing files slows down the deduplication process.
For any single D2D NAS share there are specific limits as to how many "Open Files" can be open
at any one time – this is because of the memory allocation within the D2D Backup System. Generally,
typical Filesystem backups like CommVault will open a single large container one at a time , but
it is possible due to overlapping operations that two may be open at the same time for a small
period of time. It is important NOT to send too many backup jobs to the same NAS share to avoid
exceeding the NAS > 24MB open file limit per share and per appliance. (Appliance is the whole
D2D Backup System). Failure to observe these limits can result in unstable operation. Stay within
the recommended concurrent operations above to prevent this.
For example: A D2D4312 has 4 shares configured on it. We are running filesystem backups which
open up a single container file at a time. The maximum number of backup jobs that can go to
each share is 12 so we can have a total of 48 backup jobs running simultaneously and, even
allowing for 2 files overlapping and being monitored as open at the same time, we would have
a maximum of 96 files open on the appliance in a worst case scenario. This is well within the
appliance limit of 128 open files.
HP D2D2502i HP D2D2504i
25000 25000
32 48
32 48
96 1 12
4 4
16 32
HP D2D4106 HP D2D41 12
25000 25000
64 64
64 64
128 128
6 6
48 48
HP D2D4312 HP D2D4324
25000 25000
128 128
128 128
640 640
12 12
64 64
47