Maximum size of the File System = Summation of size of all the data blocks whose addresses belongs to the node.
Given:
Size of 1 data block = 1024 Bytes
No. of addresses which 1 data block can contain = 128 (just like 128 page table entry stored in a block)
Now, Maximum File Size can be calculated as:
10 direct addresses will point to 10 data blocks in the memory = 10*1024
1 single indirect entry will point to 1 block which again points to 128 data block in the memory (just like multi level paging) = 128*1024
1 doubly indirect entry will point to 128*128 data block = 128*128*1024
1 triple indirect entry will point to 128*128*128 data block = 128*128*128*1024
Hence,
Max File Size = 10*1024 + 128*1024 + 128*128*1024 +
128*128*128*1024 Bytes
= 2113674*1024 Bytes
= 2.0157 GB ~ 2GB