TIBX overhead
I am trying to size my system partition (C:) so that a partition image will fit on a 100GB M-Disc BDXL for archival purposes. This is a GPT system with Windows 10, so I also have to make room for a 500-MiB EFI partition. 100GB should hold 95,367 MiB, so theoretically, there would be room for a C:-partition containing 94,867 MiB of data. I will not use compression, and I would like to allow for partitions that are completely full, and/or for the option to store a sector-by-sector image.
The only unknown is how much overhead there is in the TIBX files (i.e., what is the difference between the TIBX file size and the total on-disk size of the source data)? Is there any additional overhead if the backup is split (e.g., if I decide to double the partition size, or if I archive on 50-GB BD-DL media instead of BDXL)?
Obviously a safety margin can be used, but I would like to avoid making the partitions smaller than they have to be. Thus, any info on TIBX overhead would be welcome.
If I want to verify this strategy experimentally, would a sector-by-sector backup accurately represent the scenario of a fully occupied partition? (i.e., if I don't use any compression, will a sector-by-sector backup have the same size whether the sectors are empty or not?).
Is the 30% compression achieved even if the compression level is set to None in backup options? Is this 30% of the actual data size or the "size on disk" (which is larger due to cluster size)?
When I was asking about overhead, I was considering file headers and metadata that may be contained in a TIBX file. So if one does a sector-by-sector backup of, say, an 8-MiB simple volume, will the resulting .tibx file be exactly 8 MiB in size (8,388,608 bytes), or slightly larger because of embedded metadata etc.?
The 30% is an average figure one could expect to achieve when backing up a Windows OS disk with default compression settings.
A simple formatted volume will hold whatever data is written to it up to it limit. This includes metadata. The only overhead involved is the filesystem formatting and partitioning so yes, a sector by sector backup would result in that same size. Data compression has no effect on sector size.
I did some experiments.
First I created a simple NTFS volume that had a total partition size of 8 MiB, and attempted a sector-by-sector partition backup with compression set to "None". Suprisingly, the resulting .tibx file size was only 252 Kib (only 3% of the original partition size).
Second, I did a File backup of a file that was exactly 8 MiB. The resulting .tibx file had a size that was 3584 bytes larger than 8 MiB (and a "size on disk" that was one cluster -- i.e., 4096 bytes -- larger than 8 MiB). So the .tibx format does introduce some overhead (approximately 4% of the backup size for this small backup -- not sure if the overhead is fixed, or scales with backup size).
The difference is that of disk/partition vs. file/folder backup. Disk/partition backup is performed at the block or cluster level. File/folder backups are performed at the bit level. You are comparing apples to oranges.
@Enchantech,
I wasn't actually attempting to compare my "first" experiment (with disk/partition imaging) to my "second" experiment (with file/folder backup). These were two independent experiments.
The first experiment showed that when imaging a small partition, the tibx size was significantly smaller than the source partition, even though I had selected sector-by-sector backup and no compression. This was a surprise to me, as I had assumed the tibx size should be at least as large as the source partition in this case.
The second experiment showed that the tibx size was slightly larger than source file, which suggests that there is some overhead in a tibx file (at least when doing a file/folder backup).
I haven't yet been able to perform an experiment to determine whether the tibx for a disk/partition backup also includes some overhead, as the first experiment failed in this regard.
J K wrote:The first experiment showed that when imaging a small partition, the tibx size was significantly smaller than the source partition, even though I had selected sector-by-sector backup and no compression. This was a surprise to me, as I had assumed the tibx size should be at least as large as the source partition in this case.
I don't understand why you are wanting to use sector-by-sector for the image creation mode, but if you are expecting the backup size to equal the disk / partition size, then you need to select both Image creation mode options to 'Back up sector-by-sector' and 'Back up unallocated space' as otherwise you are only capturing used sectors from the source, which will be smaller.
Sector-by-sector is not normally needed unless you are dealing with a failing drive or else need to try to recover deleted files etc from such a failing drive (or for forensic purposes). ATI will switch automatically to using sector-by-sector if bad sectors are detected etc.
The size of metadata used by ATI is best represented by the small 12KB .tibx file that ATI creates when continuing backup chains, which is used solely for metadata.
See the following KB documents published by Acronis with regards to .tibx files.
KB 63518: Acronis True Image 2020: do not delete first tibx file
KB 63227: Acronis True Image: Do not delete .TIB or .TIBX files outside of Acronis True Image
KB 63498: Acronis True Image 2020: new tibx backup format FAQ
KB 63425: Acronis True Image 2020: Limitations of tibx backups
KB 63445: Acronis True Image 2020: how to view and manage backup versions in new backup format
KB 63444: Acronis True Image 2020: tibx backups in local destinations
KB 63613: Acronis True Image: local backups are not available for recovery if "metadata" file appears in the backup destination - if you see metadata file(s).
Steve,
I don't understand why you are wanting to use sector-by-sector for the image creation mode,
I tried to explain this in the first paragraph of the OP. Basically, I'm trying to simulate the worst-case-scenario, to estimate an upper bound for the tibx file size when imaging my system partitions. I was hoping this would allow me to design the partition size so that its backup image would be guaranteed to always fit on a single 100-GB BDXL disc.
However, further reading about the UDF file system for optical discs leads me to believe that the space available for data storage on optical media may not always be predictable, if extra space is used up during writing for error correction purposes. If that is the case, my original question is moot.
I'm curious about the following two "limitations of tibx" listed in KB 63425 (that was linked by Steve in Post #7 above):
- The option "Removable media settings" is available for backups in the new format, but does not take effect
- Compression level is available in backup options in the new format, but does not take effect.
Is the above (still) true in ATI2021? So if doing a disk/partition image (which automatically produces a backup file in tibx format), it is not possible for the user to control the compression level, or to modify removable media settings (e.g., disabling the Insert First Media prompt)? Or has this functionality been added to ATI2021 since the KB articel was written in August, 2020?
J K, KB 63425 is very clear that these limitations apply to ATI 2021...
Acronis True Image backups in TIBX format have the following limitations in Acronis True Image 2021:
- The option "Backup reserve copy" is not available for backups in the new format - you can use Replication instead
- The option "Removable media settings" is available for backups in the new format, but does not take effect
- Restoration from a manually moved .tibx (via Windows Explorer or other file management tools) is not possible, if all other .tibx - parts of the backup archive - were not moved too into the same folder, even if the moved .tibx contained a full backup (the term "full backup" here refers to the "full" backup type, as opposed to "incremental" and "differential" backup types)
- Compression level is available in backup options in the new format, but does not take effect.
Steve,
KB 63425 is equally clear in stating that some of the limitations may be removed in the future (relative to the date of the KB article, which was last updated on 2020-08-20):
The listed functionality may be added for TIBX backups in the future versions of the product.
(emphasis mine)
It wasn't clear to me whether "versions" refers only to major releases (i.e., we have to wait for ATI2022 to have compression options), or whether it was possible that some of these limitations had been fixed in the updates released for ATI2021 since 2020-08-20 (Builds 32010, 34340, or 35860). Hence my question in Post #9.
The lack of options to disable compression of archival images is especially concerning. Does Acronis have any internal change requests to restore this functionality that I can vote for?
Any changes to ATI 2021 via new builds are published in the associated release notes which you will find at the top of the forum via the 'sticky' posts published there by Ekaterina.
Eg: Acronis True Image 2021 Update 3 is available!
Unfortunately when a new build is released, the links to the previous release notes are lost and only the link to the latest notes are available!!
There is no published list of any internal change requests provided by Acronis other than those that can be found within forum posts. I have not seen any related to compression.
Acronis True Image backups in TIBX format have the following limitations in Acronis True Image 2021:
- The option "Backup reserve copy" is not available for backups in the new format - you can use Replication instead
- The option "Removable media settings" is available for backups in the new format, but does not take effect
- Restoration from a manually moved .tibx (via Windows Explorer or other file management tools) is not possible, if all other .tibx - parts of the backup archive - were not moved too into the same folder, even if the moved .tibx contained a full backup (the term "full backup" here refers to the "full" backup type, as opposed to "incremental" and "differential" backup types)
- Compression level is available in backup options in the new format, but does not take effect.
Wow, that made me laughing hard. There are four options that are not working for the new TIBX format, but there is no surface option to use the old TIB format still in the second version after the introduction of TIBX ? That is ridiculous for a professional software.
I was a big fan of ATI for more than 17 years, but how ATI changed in the last years is disappointing.
It became bloatware, first the malware protection (in a way ok), but now the virus protection, both without the option not to install it. A lot of people lose their trust in Acronis. Acronis was becoming great when they concentrated on making the best solution for one purpose: backup and recover files/images.
BTW: Thanks, Steve and the other, for your support here in the forum. It is strange that the MVPs are not asked/heard for the changes that were going on at ATI.