Chapter Three
File Systems and Management of Data Storages
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Guidelines and tips
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
It's all about system and network administration and the management and storage of file to different users
Typology: Cheat Sheet
2022/2023
1 / 21
This page cannot be seen from the preview
Don't miss anything!
Related documents
Partial preview of the text
Download User and group privilege and more Cheat Sheet Statistics in PDF only on Docsity!
Chapter Three
File Systems and Management of Data Storages
Outline
File System Administration
(^) Disk Partitions Mounting File Systems (^) Determining Disk Usage
Logical Volume Management (LVM) and RAID
(^) LVM Concepts (^) RAID Concepts
File System Administration…
Partitioning
Way of dividing up a disk into usable separate chunks of
known size, i.e. virtual disks
Is the lowest possible level of disk management
There has to be at least one partition in Linux
Systems that allow partitions implement them by writing a
“label” at the beginning of the disk
(^) Used to define the range of blocks included in each partition (^) Coexists with extra information such as a name or unique ID that identifies the disk
The device driver responsible for representing the disk reads
the label and uses the partition table to calculate the physical
location of each partition
4
Partitioning…
Why do we need partitions?
(^) To protect the system from users (^) Dual boot configurations (^) For backups
Linux has different partitions types
ID Description 82 Linux swap/Solaris 83 Linux da Non-FS data (used for software RAID) fd Linux RAID auto detect (previously used for software RAID) 8e Linux LVM c W95 FAT32 LBA) 7 HPFS/NTFS
Partitioning…
parted
(^) Fancier command-line tool that understands several level formats (^) Can move and resize partitions in addition to simply creating and deleting them (^) gparted is GUI version
Suggestions for partitioning
(^) Provide a separate partition for the file system containing the /home directory (^) Give enough space for the OS (^) On server systems, it may make sense to provide separate partitions for /tmp, /var and possibly /srv (^) If there are several (physical) hard disks, it can be useful to speared the system across the available disks. (^) Helps to increase the access speed to individual components 7
Mounting File Systems
Making a particular file system accessible at a certain point in
the Linux directory tree.
Allows to place a file system anywhere in the directory tree
Select a mount point
(^) $mount /dev/device /direcory/to/moount
Automatically mounting (attaching)
(^) /etc/fstab
Unmounting (detaching) file systems
(^) $unmount /directory/to/mount
Disk Usage…
(^) df (^) Summarizes the free disk space by file system (^) du (^) Summarizes disk usage by directory (^) ln (^) Used to generate links between files (^) tar (^) Archiving utility (^) find (^) Find files or patterns of files (^) fsck (^) Attempts to verify that all links and blocks are correctly tied together (^) fdisk (^) Managing partitions (^) Mke2fs (^) Creating file systems (^) mkswap (^) Creating swap file system
Common commands for file management
Logical Volume Management (LVM) and RAID
RAID (Redundant Arrays of Independent Drives or Inexpensive
Disks)
(^) Is a system that distributes or replicates data across multiple disks (^) Helps to avoid data loss (^) Minimizes the downtime associated with hardware failures (often to zero) (^) Potentially increases performance (^) Older and less used (^) Could be implemented by (^) Dedicated hardware that presents a group of hard disks to the OS as a single composite drive (^) Dominant in the past because of (^) Lack of software alternatives (no direct OS support for RAID) (^) Hardware’s ability to buffer writes in some form of nonvolatile memory (^) The OS’s reading or writing multiple disks according the rules of RAID 11
RAID…
Levels
(^) RAID is traditionally described in terms of levels (^) Specify the exact details of the parallelism and redundancy implemented by an array (^) Higher levels are not necessarily better (^) levels are just different configurations (^) In the following description (^) Numbers identify striping (process of splitting consecutive segments of logically sequential data on different disks) (^) Letters a, b, and c identify data blocks with in a striping (^) Blocks marked q and p are parity blocks (^) Linear mode or just a bunch of disks (JBOD) (^) Not a real RAID (^) Concatenates the block addresses of multiple drives to create a single larger virtual disk (^) Provides no data redundancy or performance benefit 13
RAID Levels…
RAID Level 0
(^) Used strictly to increase performance (^) Combines two or more drives of equal size (^) It strips data alternately among the disks in the pool Sequential reads and writes are spread among several disks (^) Decreases write and access times (^) Has low reliability compared to separate disks
RAID Levels…
RAID Level 1+0 and 0+
(^) Are stripes of mirror or mirrors of stripe sets (^) Are concatenations of RAID 0 and RAID 1 (^) Have support by many controllers and software implementations Goal (^) Obtain the performance of RAID 0 and redundancy of RAID 1
RAID Levels…
RAID Level 5
(^) Stripes both data and parity information, adding redundancy while simultaneously improving read performance (^) Writes data blocks to N-1 disks and parity blocks to the Nth^ disk (^) More efficient in its use of disk space than RAID 1 (^) If there are N drives in an array (at least three are required), N-1 of them can store data (^) The space efficiency of RAID 5 is therefore at least 67%, whereas that of mirroring cannot be higher than 50%
Logical Volume Management
Limitations of partitions
(^) Partitions are inflexible (^) Hard to resize partitions (^) Adding disks and partitions spread data (^) Makes consolidating backups difficult
Solutions
(^) Logical volume management (^) Merges one or more partitions or devices into a single logical volume group (^) Allows to dynamically create, resize and delete volumes in a volume group (^) Removes the need to unmounts volumes or reboot the system to update the partition map
Logical Volume Management…
LVM system has three layers
(^) Physical volumes (^) The bottom layers (^) Consists of disks, partitions or RAID arrays (^) Volume groups (^) Created using physical volumes (^) Consist of one or more physical volumes (^) Logical volumes (^) Created from the space within a volume groups (^) Are the LVM equivalent of partitions (^) Can hold arbitrary file systems or swap space