Technical information

June 2012 Dell EqualLogic Configuration Guide v13.2 81
Referring to
File System 1 in Figure 30, you could assign any of the three file system security styles to
it. Given that portions of it are simultaneously accessible as CIFs shares and NFS exports, a general rule
of thumb for how to assign the security style would be as follows:
• If your users are predominantly Linux/UNIX based, use the UNIX style.
• Likewise, if your users are predominantly Windows/CIFS based, use the NTFS style.
• If you have a nearly even mix, then use the mixed style.
6.4 File System Snapshots
Dell FluidFS snapshots are created and managed by the FS Series appliance to provide a file system
level snapshot capability. They are read-only and are created using a redirect-on-write method. This
method is also referred to as allocate-on-write. This approach requires only one I/O operation and
delivers higher write performance.
Additional FluidFS snapshot limits and considerations:
• Each NAS File System has its own snapshot policy.
• The minimum unit a snapshot can act on is a NAS File System.
• The maximum number of snapshots you can retain per file system is 512. The maximum
snapshots retained per FS7500 appliance cluster is 10,000.
• When you create a snapshot, all shares and exports within that file system are included. If a
particular share or export will require frequent snapshots, you should group it with others that
have the same requirement, or dedicate a file system to that particular share or export.
• The FluidFS snapshot implementation allows for end users to individually select and restore
previous versions of files. The .snapshot directory contains all the snapshots taken for the file
system. Browse to the correct snapshot directory to access the files needed to be restored to
the share. Windows users can also use the “Previous Version” feature of Windows files and
directories to restore individual files or entire folders.
Sizing limits and space utilization considerations for FluidFS snapshots:
• The size of the snapshot reserve is specified as a percent of the file system size. It is set at file
system creation and changes according to the % reserve setting whenever the size of the file
system is changed.
• The default snapshot reserve size is 50%. It is common to select a reserve size in the range of
25%. The maximum snapshot reserve size is 90% of the FS size.
• The snapshot reserve capacity is counted against the NAS file system reserve space. However,
the snapshot reserve space is not enforced. File system data can fill the snapshot reserve
space.
Note: FS Series FluidFS snapshots and PS Series volume based snapshots function independently
and have no impact on each other. Please see the following whitepaper for more information on
Dell FluidFS snapshot behavior:
Dell Scalable File System:
http://www.dellstorage.com/WorkArea/DownloadAsset.aspx?id=1578