EXT3 file system: the essence, compilation, correction of errors, restoration of damaged data, the final result

In computing, the file system is used for management. Without it, the information placed in the storage area will be one large amount of data without the possibility of indicating where one piece of information stops and the next begins. Dividing information into separate parts and providing each part of the name allows it to be easily placed, transferred and identified. The structure and logical conditions used to manage information groups and their names are called the “file system”. Today users can access files: F2FS, EXT4, VFAT, Fat32, Exhibit, EXT3, EXT2, NTFS.

File system varieties

EXT2 Files - This was the first commercial Linux system that did not support logging. Suitable for SD cards and USB drives, as it has high performance and low recording volume. USB and SD storage are limited to write cycles, so this format is best suited for them. Limits:

1. Individual file size from 16 GB to 2 TB.
2. System size 2TB to 32TB.
3. Limits are calculated based on the block size used.
4. The block size varies from 1 KB to 8 KB. For example, if a block size of 1 KB is used, the maximum file size can go up to 16 GB, and for 8 KB - 2 TB.
5. The average range size is 2 KB and 4 KB, which has a file size of 256 GB and 2 TB.

The EXT3 file system is designed to overcome the limitations of EXT2 with logging support. It tracks file changes that help in fast recovery and reduce the likelihood of data loss in the event of a system failure.

Limits:

1. Individual file size from 16 GB to 2 TB.
2. Size 4TB to 32TB.
3. Update FS from EXT2 to EXT3.
4. EXT4 is the fourth advanced system designed to overcome the limitations of EXT3, introduced in 2008 by a development team. The latest version in the ext family with logging support and many new features.
5. Backward compatibility.
6. Constant pre-selection to select a file system.
7. Delayed selection.
8. Unlimited subdirectories.
9. Checksum log.
10. Quick check FS.
11. Transparent encryption.
12. Limits: individual file size from 16 GB to 16 TB. Size up to 1EB.
13. No FS update required. Due to backward compatibility of EXT2, EXT3 can be directly mounted as EXT4.

Linux FS: file system EXT2, EXT3, EXT4.

Features of EXT3 Files

EXT3 extends the popular EXT2 with the introduction of the magazine. This is essentially an “intention to capture” data. The amount of information recorded is adjusted and varied to record what is known as “metadata”. After updating the journal, the system records the actual data in the appropriate areas and marks the journal entry to record it.

After a crash, the system can be returned very quickly online, using a log that reduces the number of minutes using fsck, with the added benefit of a significantly lower chance of data loss or corruption. When a file is connected to a file, the last snapshot of this file is read from disk to memory. At certain points, the EXT3 file system will update disk file data from incomplete journal entries and trim these journal entries.

Copying operations and synchronizing them in a log with an associated system is called a checkpoint. It usually changes by formatting the storage in a different format and using a PC, or by user recovery. A recovery such as TWRP does not allow them to be changed by default, while CWM recovery allows the user to select a system without additional effort. Available systems are determined by the kernel developer.

Formation process

File system - a method of organizing information on a computer. On Linux and other Unix-like systems, for example, the Android file system, the basis is the directory hierarchy, which begins with the root directory and is indicated by a slash and contains a series of subdirectories, each of which, in turn, may contain additional ones. EXT2 is the simplest and most portable of native Linux systems because it is the easiest way to transfer data. It was developed as an improved version of an extended system and was included in the core of the OS and is still widely used.

The journal form maintains a special file called the journal, which is used to repair any inconsistencies that result from an incorrect shutdown of the computer and thus always maintain internal consistency. Such outages usually occur due to a power outage or a software failure that cannot be resolved without a reboot.

The EXT3 file system adds to its predecessor:

1. Journal.
2. H-tree (hashed tree) directory indexes.
3. Types of files in a directory.

Without them, any EXT3 file system is actually an EXT2 file system. This allowed the use of proven and mature file system maintenance utilities (such as fsck) to support and repair EXT2 file systems that can be used in EXT3 without significant changes.

Logging Options

The EXT3 log must not be on the same physical device as the file system that it logs. On RedHat Linux, the journal device can be specified using the journal_device = parameter, with the -journal-options command line argument to tune2fs.

The EXT3 file system provides three options:

1. Writeback is fast for the price of limited data integrity. Allows you to display old data in files after a crash and rely on standard kernel backups to flush buffers.
2. Ordered data is compatible with the system - new files that do not contain garbage after a crash.
3. Logs are data that requires more space and lower performance. The safest data storage policy.

The problem of using the system

If a user creates a Linux EXT3 system on an entire disk that is not initialized, there is a risk of failure because it is not created on the partition, but on the second SCSI disk. Before fixing a file system error, the following operations are performed:

1. Enter: fdisk -l / dev / sdb.
2. An ext3 system is created with the volume label “/ newfs” on a hard disk without a partition: mkfs -t ext3 -L / newfs -v / dev / sdb.
3. A new ext3 system is installed: mount -t ext3 / dev / sdb / newfs.
4. Run umount / newfs: mount -t ext3 LABEL = / newfs / newfs.
5. It is better to create an EXT3 system on a partition rather than directly on the hard drive if the second SCSI hard drive was initialized by one main Linux partition before running the mkfs command.
6. Run: fdisk / dev / sdb, mark “n” to add a new partition “p” for the main partition, “1”.
7. For partition number 1, before correcting a file system error, press ENTER twice to accept the default value and efficiently allocate the entire hard disk for the main partition, “w”, and create a partition table.
8. Run mkfs -t ext3 -L / newfs -v / dev / sdb1 to create an EXT3 system on the main partition (/ dev / sdb1).
9. Now one of these two mount commands will work without errors: mount -t ext3 / dev / sdb1 / newfs mount -t ext3 LABEL = / newfs / newfs, after adding this line to / etc / fstab: LABEL = / newfs / newfs ext3 default.
10. Linux will then automatically mount this new system each time it reboots, or you can start it through mount / newfs at the root command prompt.

You can use File ScavengerTM to recover data from an external volume when it becomes damaged or accidentally deleted. In these situations, the file system metadata remains intact, and recovery is possible. Raw recovery is possible for the ext4 volume when deleting a file or reformatting the volume.

Another great data recovery program is Quick Recovery for Linux. This is a convenient tool for users who are faced with data loss in the Linux operating system. The software works in fully automatic mode and provides fast recovery for files lost during accidental deletion, physical damage, OS failure, logical errors, incorrect shutdown and much more. It genuinely restores all deleted, damaged, formatted or lost data from any of the data loss events.

Fix delay issues

EXT3, being the standard for almost all installed Linux systems, including the Android file system, is quite well tuned for performance. However, some performance problems in EXT3 do occur, especially in places where the fsync () system call is used. The problem is that EXT3 starts in data mode, when some processes call fsync () to clear the data on disk. This problem is best known, for example, in the form of system braking Firefox.

The first fix is ​​to mark the I / O requests generated by fsync () with the operational bit WRITE_SYNC, marking them as synchronous requests. The CFQ I / O Scheduler starts synchronous requests. Typically, reading is considered synchronous, but not writing. Once synchronized fsync () requests are synchronized, they will be able to move on to normal I / O.

This makes fsync () much faster by slowing down tasks that require I / O on the system. In addition, the CFQ scheduler uses “forward” logic with synchronous requests. After executing one such request, it will stop the queue to see if a neighboring request appears. The idea is that the disk head will be perfectly positioned to satisfy this request.

Ext2Fsd File Downloader

You can install Ext2Fsd on a Windows computer, and it will provide access to these systems. This simple tool supports the following features:

1. Read access to ext2 / ext3.
2. Repeated playback of ext3 log during installation.
3. Mount point settings.
4. Inode Size: 128, 256.
5. File size is greater than 4G.
6. Sharing CIFS over a network.
7. Indexing directories htree.

Works with Windows 2000 / XP / 7.

Program installation:

1. Download the installer package. If a compressed version of the file has been downloaded, unzip it.
2. Double-click on the file Ext2Fsd-XXX.exe (XXX is the release number).
3. Complete the first steps of the installation wizard.
4. When the “Select Additional Tasks” screen is reached, check all three windows and click the “Next” button.
5. Complete the installation wizard (the remaining steps are standard).

Enabling file installation on Windows

After the ext2 / 3 drive is connected, the PC will not see anything. The user needs to tell the application how to handle the disk manually by assigning a disk. This can be done in one of three ways:

1. Insert a disk using a special adapter that allows you to connect the drive to a USB port on the device. It doesn't matter how it is done if the machine recognizes a physical disk. Launch the app.
2. Go to the beginning of All Programs, then | Ext2Fsd | Ext2 Volume Manager to run.
3. When the main application window opens, find the newly connected drive, it will have the EXT2, EXT3 file system.
4. Click OK.
5. Click the Finish button.

If the user right-clicks the same drive and selects the “Ext2 Management” option, you can configure this drive at a narrower level. The following options are available:

1. The volume is read-only.
2. Installing a read-only disk Codepage.
3. Changing the code page of a disk, for example, iso8859-1, utf8, acsii, etc.
4. Installing a drive and letter: select the drive to automatically mount and the name of the drive.

Direct use of documents Win7 / 8/10

If you are using a PC with two Windows and GNU installed. Linux OS stores many documents, music files and movies on ext3 / ext4, the user can read and use them directly from Windows. Below are a few programs that allow you to mount the EXT3 file system on Windows (free):

1. Ext2Explore (also known as Ext2Read) is probably the best historically known Windows driver that makes Linux ext FS reader Explore2FS - a tool for analyzing the GUI and access to ext2 and ext3. It works under all versions of Windows and can read almost any system.
2. Disk Internals Linux reader is a free tool for reading and extracting files from EXT2 / EXT3 / EXT4, HFS, UFS2, Reiser4 and ReiserFS partitions on Windows.
3. ParagonExtFS is a proprietary software with a version for Win OS and Mac (it also supports the installation of Linux blocks for Mac). Read copy files from Mac OS HFS + on Windows. Apple has a Boot Camp driver package that allows Mac OS HFS + to be visible from Windows.

For people who do not intend to constantly read HFS + data, it is better not to download Boot Camp, but to use HFSExplorer and the final flash file system.

Boot Camp and HFSExplorer allow you to read data from a Mac OS system read-only. If you need to write to the HFS + system from Windows, you will need: Native Paragon HFS + (or) MacDrive from Mediafour

Resolving Acronis File Crash

Acronis Disk Director can split a disk into as many parts as necessary, while data is not lost. The program makes it easy to convert, combine, divide and resize volumes. It also makes it easy to copy files and volumes to where they are needed. The user interface makes it easy to complete tasks thanks to an intuitive design. It can format a disk from any of the following systems: FAT32, EXT2, EXT3.

However, there are times when the EXT3 file system crashes after Acronis. One of the reasons for Acronis EXT2, EXT3 partition backup errors, when some partitions contain errors and can be displayed only by sectors, may result in system damage. Correction of this type of failure can be done by backing up Ext2, Ext3 Linux partitions. You need to check the section for bad blocks: -vs / dev / sda 99.

The next failure is the error "the source disk cannot be empty." Problem: A single drive from a RAID array dies using an Acronis boot disk that tries to create a RAID backup and generates an error "source drive cannot be empty." To fix the damage to the file system, if the system does not boot, try autoload, then perform backup under Windows, and if this does not help, then use the approach to backup by sector.

As you can see, the control system is used by the user in the form of a registered database of information that is easily placed, transferred and identified. The newly created journal form, which is indispensable in restoring any inconsistencies in the computer, provides internal consistency - this is the essence of the EXT3 file system.