Category Archives: Windows

How to handle “Data error (cyclic redundancy check)” (system error code 23)

Posted on by
Reply

If you get an error like this during image backups:

Error on client occurred: Error while reading from shadow copy device (1). Data error (cyclic redundancy check).

Or like this during a file backup:

Error getting file patch for “x/y/z.file” from CLIENT. Errorcode: ERRORCODES (11)
Remote Error: Reading from file failed. System error code: 23

Or you get the same error while copying/accessing a file in any program (Windows Explorer, etc.) you have damaged sectors on your hard disk. One way to confirm this is to have a look at your disk’s S.M.A.R.T. values (e.g. with SpeedFan; please comment with a better alternative if you have any).

The raw value of “Current pending sector count” should be greater than zero.

As an explanation: Your hard disk is designed such that the probability that each sector becomes unreadable is really low. Nevertheless, it is still possible and expected during a hard disk’s lifetime, as such the hard disk is engineered to handle this failure case. The hard disk has a few spare sectors. If a sector becomes damaged, the hard disk replaces this sector with one of those spare sectors. The good case is that the hard disk detects that a sector has problems while still being able to read the data in this sector (e.g. by retrying or using storage redundancy). In this case it can read the data, replace the sector with a spare one, write the data to the spare sector and use the spare sector from then on (S.M.A.R.T. value “Reallocated Sector Count” is increased by one).
If it cannot read the data it has to return a error saying that it cannot read the sector (and increase “Current Pending Sector Count” by one). The next time the sector is written to, it’ll write the data to a spare sector, then replace the damaged sector with the spare one (and decrease “Current Pending Sector Count” by one while increasing “Reallocated Sector Count” by one).
The error being returned by Windows if the hard disk says a sector is unreadable is “Data error (cyclic redundancy check)” (system error code 23).


If you don’t have a copy of the damaged sector you have lost data. You could retry a few times. Put the hard disk in a freezer and then retry or something, but chances are it won’t work.

This doesn’t mean your hard disk is completely broken. It may be an indication that it is going to break completely soon, but you also might have just been unlucky during normal operation.

How to fix it

If the error message includes a file path, replace the file with a backup copy. If you don’t have a backup copy, you can either delete the whole file, or use the scrub tool below to only delete the damaged parts of the file (if it is a movie file or an image it might be mostly okay).

If it is occurring during image backups, the scrub tool has the option to find out which files are damaged. You can then either replace the files with backup copies, delete the files or let the scrub tool delete the damaged parts of the file.

If the damaged files are Windows system files, they might get fixed by running a system integrity check. Open an admin console (WINDOWS + X then “Windows PowerShell (Administrator)”) then enter “sfc /scannow”.

Scrub tool

The UrBackup client (starting with 2.4.x) includes a tool that scans a whole disk, then lists the damaged files, then has the option to delete damaged parts of a file.

  • Download and install UrBackup client from https://www.urbackup.org/download.html#client_windows
  • Go to “C:\Program Files\UrBackup” in Explorer
  • Right-click “scrub_disk.bat” then select “Run as Administrator”
  • Select the volume you want to repair
  • If it finds unreadable sectors it asks if you want to list the damaged files (this might take some time) and if you want to delete those unreadable sectors

UrBackup Windows Installer creator

Posted on by
1

If you wanted to create a generic UrBackup client installer for your internet server you’d have to create one yourself following instructions here .

I have made https://installercreator.urbackup.org/ to make this process easier. Given the correct parameters it’ll create a executable for you that’ll create a client on your server, then download the client installer for this newly created client and then run this installer. It’ll use the computer name as default client name, optionally appending a random string, such that name collisions do not occur.

Image mounting in UrBackup Server 2.1.x

Posted on by
6

UrBackup 2.1.x can now mount image backups. That is, it lists the image backups it has on the web interface, you can browse into them and e.g. download files or directories as a ZIP file.
I am particularly proud that this works on Linux as well as on Windows with both raw image files and VHD(z) files. On FreeBSD it only works with raw image files currently. The screenshots are from a Windows UrBackup server.

On Linux it uses libguestfs-tools to mount images in a sandboxed virtual machine. On Windows/FreeBSD mounting a hostile image may be a dangerous operation.

Windows Backup API support in UrBackup 2.1.x

Posted on by
2

UrBackup 2.1.x has more completselect_windows_componentse Windows Backup API support. Previously the backup API was only used to create snapshots of the specified paths to backup (volume shadow copy snapshots). Now it does a so called component level backup, if configured to do so. You can select the components to backup via the client user interface and then the selected components automatically communicate to UrBackup which files need to be backed up, and on restore it communicates where the files should be restored and if e.g. services should be restarted during/after restore.select_restore_components

This works with applications which in turn support the Windows Backup API, such as for example Microsoft Exchange, Microsoft SQL Server, Microsoft Hyper-V, Oracle DB on Windows.

Testing backup and resrestore_componentstore with those different applications is now the big item on the to-do list. Every help and pointers to applications where backup or restore is broken will be helpful.

Visual Studio 2015 runtime and MSI installer

Posted on by
3

If you are using the MSI installer to install either UrBackup Client or Server on Windows there is a potential problem you might run into.

Starting with Visual Studio 2015, with which UrBackup Client/Server 2.x are compiled, Microsoft decided to split the Visual Studio runtime into a operating system level component (Universal Runtime) and another “normal” runtime component, wheras earlier it was only a “normal” runtime component.
The operating system component is installed via Windows Update and cannot be installed by a MSI installer. With Windows 10 it is always installed, but with Windows Vista or 8.1 the system needs to be up to date in order for the system component to be present (KB2999226), otherwise UrBackup will not start.

Another work-around is to use the .EXE (NSIS) Installer which includes the operating system compontent. Installation depends on Windows Update functioning correctly (which it may not).

Let’s just say this change does not make the software developer’s and user’s life easier.

New in UrBackup 2.0.x

Posted on by
3

Wactivitieseb interface modernization. The web interface was a little bit utilitarian which gave many people the wrong impression. With the help of mombojuice the web interface was improved such that it looks much more modern and professional. Many small improvements were made as well. For example the dates are now formatted according to browser locale, backups can be started via drop-down menu and the live log of a running backup can be directly accessed from the activities screen.

Improved file deduplication. Completely reworked the file deduplication and file backup statistics calculation. This should be much faster, scalable and reliable now.

File lastmodifiedbackup improvements. File meta-data such as last modified time and file permissions are now backed up on all supported client systems (Windows, Linux, Mac OS X). Supporting more exotic file system features such as sparse files UrBackup is now a fully featured file backup solution.

File backup restore. To restore the file meta-data UrBackup has now an integrated file restore. The file restore reuses client-side hashes, if present, and transfers only differences, such that restoring folders with only few changes since the restored backup is fast.

access_backupsDirect backup access. If configured, the backed up file permissions are used to allow clients direct access to their files with only minimal configuration. On Windows there is a shortcut in Explorer which directly opens the relevant/file folder in the browser. There is a new list view which shows a file/folder in all backups. For files, hashes are used to show when the file content changed (versions).

image_backup_settingsImage backup improvements. UrBackup supports GPT formatted disks now and the restore CD boots on UEFI firmware devices (also with secure boot enabled). In combination with btrfs, UrBackup supports an incremental forever style image backup and image backups over 2TB. For VHD/VHDZ UrBackup has now settings to base incremental backups on the last or last full image backup. Full image backups can be configured to be synthetic full backups transferring only changes since the last image backup.

Significant security improvements. Forward secrecy for Internet clients via ECDH and Internet client security improvement by using AES-GCM. Switch from DSA to ECDSA for client update and server identity signatures. Web server/restore CD login now uses PBKDF2.

Mac OS X client. There is nowmac_backup_running a UrBackup Client for Mac OS X. This client is fully featured, excluding image backup (like Linux client). The Mac OS X client can be used as a technically superior backup solution to Time Machine.

Improved command line. Mainlttyy for Linux all command line usage has been significantly improved. This includes the command line client (urbackupclientctl), the server command line (urbackupsrv) and the restore client.

Linux file system snapshotting. Snapshotting now also works on Linux and is fully integrated. A portable Linux client includes snapshot scripts for LVM, dattobd and btrfs which work without changes in most cases.

Lots of other changes. Proper symbolic link backup. Virtual clients allow you to backup different sets of files at different intervals and max/min amounts. Simultaneous image and file backups. Different backup speeds and backup intervals at different times. Improved Internet transfer compression. New hashing method where the server only needs to hash changed parts of a file.

 

Can you use the last modified file time on Windows as change indicator for incremental file backups?

Posted on by
Reply

Short answer: No.

If your backup software is using the last modified time on Windows as the only indication if a file changed or not the backup software will miss some changed files.

The first issue is that Windows does not update the last modified time until the file is closed by the program writing to it. To work around that your program will need to track which files are open when a shadow copy is created.

The second less known issue is that last modified times are not changed at all if a file is modified by memory mapping it and then modifying it via memory mapping. This isn’t just an edge case – Windows itself creates such files, as well as e.g. Microsoft Exchange and other performance sensitive applications.

UrBackup handles both cases during incremental backups, many other backup software does not.

Start of UrBackup 2.0 beta phase

Posted on by
Reply

UrBackup Server/Client/Restore 2.0.0 beta was recently released. This marks the beginning of the UrBackup 2.0 beta phase.

See the forums for download links and discussion.

UrBackup 2.0 marks the beginning of UrBackup having no major limitations. If you still find some please start a discussion in the forums. The next beta version will also properly support sparse file backup.

Progress update on the next major UrBackup version

Posted on by
6

Currently the next major UrBackup version is kind of close to getting finished. There are a few major work in progress areas. Once they are finished and I have done some overall testing I will release a beta version.

The major changes in the new version are:

  • Completely reworked the file deduplication and file backup statistics calculation. This should be much faster, scalable and reliable now.
  • The Copy-on-Write image backups on btrfs mentioned in the last post. Synthetic full backups for the VHD/VHDZ file format and settings for basing image backups on the last full or last incremental backup (differential/incremental).
  • File backups include file metadata including file modification time, ACLs, alternate data streams etc.
  • Backup of streaming data. E.g. the output of “mysqldump”/”pg_dump”. I plan to add basic backup scripts for popular Open Source databases to the client
  • New file restore feature which restores file backups and properly restores the file meta-data
  • The ACLs/file permissions are used to enable users to directly access backups on the web interface from the explorer on the clients (via right click -> Access/Restore backups)
  • Proper backups of symbolic links. Symbolic links which point to folders/files which are backed up are backed up as symbolic links and symbolic links which point outside of the selected backup set are followed/not followed depending on a setting
  • The web interface has been bootstrapified (http://getbootstrap.com/ – mombojuice did the work) and looks much more modern now
  • Simultaneous image and file backups
  • Backup and restore EFI boot sector and partition on UEFI systems. Restore CD that boots with UEFI firmware
  • Client for Mac OS X
  • Forward secrecy for Internet clients via ECDH and Internet client security improvement by using AES-GCM
  • Switch from DSA to ECDSA for client update and server identity signatures

Still to do:

  • Lot’s of testing and bug fixing
  • Backup and restore of file meta-data on Mac OS X and Linux
  • Symbolic link backup handling on Mac OS X and Linux
  • Automatic client update for Mac OS X like for Windows
  • Restoring files which are in use on Windows (via restarting)
  • Update Documentation

Remaining UrBackup limitations (to be done after with a subsequent version):

  • Recognize hard links and backup the files only once
  • Backup only used areas of sparse files
  • Continuous file backup

Once the “to do”s are done this is a big step forward for UrBackup. Having streaming file backups and incremental, differential, synthetic full and full image backups basically allows you to implement pretty much every backup strategy with UrBackup. The only thing missing is the continuous file backup and I already started work on that.

For example you could use UrBackup instead of TimeMachine on Mac OS X and do a full system restore via the file restore feature (this is not implemented at all – it is just an example what it might be able to do). You probably don’t even need an image of your Windows system partition but can restore it via the file backup restore (albeit inefficiently, because the hard links in C:\windows\winsxs are not handled properly).

Performance considerations for larger UrBackup server instances

Posted on by
4

If you are planning on setting up a larger UrBackup server instance you will find some hints about performance in this post. “Large” in this context is difficult to define, because it depends on the number of clients, the number of files and file sizes in the backups and the backup intervals.

If you plan on setting up a “larger” UrBackup instance you should keep the following things in mind:

  • UrBackup uses an internal (SQLite) database. This database could cause performance problems, especially with a large number of backed-up files and full file backups. The database should be stored on storage suited for databases.
  • UrBackup has some tuning options, but is nevertheless pretty optimized per default. You should only have to tune UrBackup in special circumstances. You will find information about the tuning options in the administration manual.
  • There are many platform options and each has its own considerations, so you should read up on the platform-specific performance considerations. For example you should not run FreeNAS virtualized.

Your system will almost certainly be IO limited. If you have a running system you can verify that by looking at the performance monitor on Windows, iostat on Linux and zfs iostat on FreeBSD. Often it is limited by random read/write performance (Input/Output operations per second).

If you want maximum IO performance following should therefore be the case:

  • The UrBackup database should be on an SSD. This should be a no-brainer, as this database does not get too large and SSDs are way faster than spinning disks. The random reads/writes are for example 900 times faster with a Samsung 840 Pro (97K IOPS).
  • The UrBackup database should not be on the same disk as the backup storage.
  • The UrBackup database should not be on a RAID-5, as this is not optimal for databases.
  • If the database is still the bottleneck (because it is a separate device you can find this out using iostat or an equivalent), you can use the “file entry cache” (see manual). This cache should be on a separate SSD, otherwise it will only cause more IO on the one device.
  • Save the filesystem metadata of your backup storage on an SSD and only the actual data on a spinning disk RAID-5/6 to get the maximum performance. This is only possible with btrfs on Linux.
  • Avoid full file backups. When doing a full file backup UrBackup has to load all files, calculate their hash value and look this value up in the database. This incurs a lot of IO on both the database and the backup storage (and the client). UrBackup can run an infinite amount of incremental file backups without any full file backups.
  • Optimize the maximum number of concurrent backups such that the throughput is maximized.

Ways to absolutely kill performance:

  • Save the UrBackup database on ZFS/btrfs on a spinning disk. Databases (those who use WAL or intent logging; including SQLite3) on ZFS/btrfs are a known pathological case for copy-on-write file systems. The database files get horribly fragmented. Btrfs has a (currently disabled per default, because it is not stable) background defragmentation for that, but ZFS does not.
  • Save the UrBackup database on a RAID-5. See http://www.baarf.com/.
  • A lot of full file backups.
  • Enable ZFS deduplication without having enough RAM for the dedup table. See here for a discussion.