Using para-virtualization can slow down memory translation for a guest OS.

One danger of hard links is dangling references to files.

You use a log-based SSD to hold your data.  The SSD has 3 blocks with 10 pages per block.  Each page holds a single character.  The SSD has been used for a while and the current state of the SSD is shown below.  The diagram for the SSD contains the following items: FTL mapping logical pages to physical pages block numberpage number (2 lines)state of each page (valid, Erased, or invalid)data stored at each pagean indicator(+) if a page is currently live (has an entry in the FTL)Current State of SSD: FTL     1:  6   2: 10   5:  2   7:  1         8: 20   9:  4  12: 16  13:  9        15: 12  17: 17  18:  5  29: 13        19: 11  20: 14  21: 15  23:  3        24: 18  25:  0  27:  8  28:  7 Block 0          1          2          Page  0000000000 1111111111 2222222222       0123456789 0123456789 0123456789 State vvvvvvvvvv vvvvvvvvvv vEEEEEEEEE Data  Ih7tj3UYbK 34quFTEPXg H          Live  ++++++++++ +++++++++  +           Operations that the OS may perform are:write(Logical Address, Data) – storing the data at the logical address read(Logical Address) – reading the data from the logical address trim(Logical Address) – deleting the data from the logical address

In a simplified file system the following operations are implemented:   mkdir() – creates a directory creat() – creates an empty file open(), write(), close() – appends a block to a file link() – creates a hard link to a file unlink() – unlinks a file   The on-disk file system is represented by the following:   inode bitmap inode table (each inode surrounded by square brackets) data bitmap data blocks (each block surrounded by square brackets)   The inode structure contains the type (d – directory, f – regular file), a pointer to a single data block (a), and a reference count (r).  A directory data block contains (filename,inode number) pairs.   The current state of the file system is as follows:   inode bitmap  11111100inodes [d a:0 r:4][d a:1 r:2][f a:-1 r:1][f a:-1 r:2][d a:2 r:2][f a:-1 r:1][][]data bitmap   11100000data [(.,0) (..,0) (g,1) (q,2) (u,3) (x,3) (t,4)][(.,1) (..,0)(c,5)] [(.,4) (..,0)][][][][][]

In data journaling, a transaction consists of a begin block, blocks for all updates to the FS, and an end block.

You see a segment with the following set of writes block 100: [(“.” 0), (“..” 0), (“foo” 1)] block 101: [size=1,ptr=100,type=d] block 102: [size=0,ptr=-,type=f] block 103: [imap: 0->XXX,1->102]    What could be the contents of XXX in the above segment?

Hardware that meets the Popek Goldberg criteria can use the trap-and-emulate model for virtualization.

Assuming we start with no state in memory, and have a LFS with that looks like the following: how many disk I/Os do we need to perform to read the contents of the directory “/”?   block 0: Checkpoint region: imap[0..2] -> 3block 1: [(“.” 0), (“..” 0)] block 2: [size=1,ptr=1,type=d] block 3: [imap: 0->2]

Direct Memory Access (DMA) orchestrates the transfer of data between main memory and  devices without much CPU intervention.

In the FFS filesystem, the system attempts to spread files within the same directory across different groups.