The original SNAP NAS devices were developed by SNAP Appliance. The operating system that was used was a flavor of BSD in concert with the file system UFS. Although the file system looks very similar to the original UFS there were some subtle changes made. View It Now takes those changes into consideration when searching and building a virtual drive. Although the majority of View It Now makes the mechanics of the file system transparent to the technician there are some things that still need to be addressed in a ‘native mode’ manner. The following are a list of options/functions that are specific to the SNAP OS 4.x version of View It Now.
Verify Cylinder Groups
The SNAP OS file system is very similar to many Linux/Unix type file systems. The file system is spread across the entire drive with many little sub-groups that maintain a microcosm of the entire file system. Some file systems call these groups ‘Allocation Groups‘, others call them ‘Block Groups‘, and this file system uses the label ‘Cylinder Groups‘.
The reason that groups are used is to allow the file system to manage the hard drive in such a way as to keep wide seeks to a minimum. For instance, if you have a database that is spread across an entire drive due to fragmentation you get the heads moving up and down across the drive which causes unnecessary heat, wear, and time to read or write data. If the data is kept in a smaller area then the drive will have shorter seeks, hopefully contiguous reads, and a more stable file system.
All of this being said each cylinder group has its own set of inodes, a data set area, a block bitmap and other system data. The report takes a look at some of the system information to try and determine if the cylinder groups are in alignment. To execute the report use the following steps.
- 1. Make sure that a volume is mounted. Refer to View It Now documentation to see how to mount a volume.
- 2. Move the mouse to the ‘Volume Tools‘ item on the menu bar and click. You will be presented with a drop-down menu.
- 3. From the drop-down menu select the item labeled ‘Verify Cylinder Groups‘ and click on it. The testing will begin.
- 4. To monitor the progress of the test look in the ‘Search Information‘ group box. The ‘Block‘ label will indicate which cylinder group is being tested, and how many total cylinder groups are in this particular volume.
- 5. Once the test is finished a dialog box will appear indication how many cylinder groups did not pass the test.
The comments below are for users to ask questions and request product updates.
View It Now Quick Start Guide
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