Virtual TapeServer 8.4 Configuration Guide

Reconfiguring Vaults | 11
system memory that is above and beyond the memory used for the operating system and
kernel.
Example for EXT3 file systems:
Checking is done using bitmaps, three for blocks, and up to six for inodes. For example, for a
ext[2,3] file system that is 5TB with a block size of 4KB, divide 5TB by 4KB and then divide by
8 bits per byte to find amount of memory needed for each block bitmap:
5497558138880 / 4096 = 1342177280 blocks
1342177280 / 8 = 167772160 bytes per block bitmap
Now, take 5TB again and divide by 8K inodes per group and then divide by 8 bits per byte to
find the amount of memory needed for each inode bitmap:
5497558138880 / 8192 = 671088640 inodes
671088640 / 8 = 83886080 bytes per inode bitmap
Finally, there are three block bitmaps and up to six inode bitmaps:
(167772160 * 3) + (83886080 * 6) = 1006632960
The file system requires approximately 1GB of free memory to run fsck (the fsck.ext[2,3]
command) if there are no directories. In addition, fsck.ext[2,3] keeps a directory information
bitmap, which requires 12 bytes for each directory.
Example for GFS file systems:
Each block of memory in the file system requires approximately one byte of additional
memory. So, to estimate the amount of memory you will need to run fsck (the gfs_fsck
command) on your file system, divide the file system size (in bytes) by the block size. For
example, for a GFS file system that is 5TB with a block size of 4KB, divide 5TB by 4KB:
5497558138880 / 4096 = 1342177280
This file system requires approximately 1.25GB of free memory to run the gfs_fsck command.
Note that if the block size was 1K, running the gfs_fsck command would require four times the
memory, or 5GB.
l All data on a partition that is resized will be lost.
Keep in mind that performance and system operations will be slow when vaults are at maximum
capacity.