Compressing a DD image - caveats and optimal settings
I have a 30GB dd image of an SD card, and am using the 7-Zip command line to compress it. Are there any particular options I should enable or avoid when it comes to a dd image that, presumably, must remain absolutely unchanged in order to ensure it can be recovered from?
For example, should solid compression be avoided? Is there a compression algorithm that's likely to compress dd images more efficiently (i.e. that offers the best trade-off between speed vs time) than any other? And so on.
Alternatively, are bit-wise images compressed in pretty much the same way as any other data would be? This is also a valid answer.
Here's what I have so far:
7z a -t7z -mx=9 -ms=on "SDcardbackup" "SDcardbackup.img"
compression 7-zip dd disk-image
asked Jan 24 at 1:33
HashimHashim
3,17163162
add a comment |
I have a 30GB dd image of an SD card, and am using the 7-Zip command line to compress it. Are there any particular options I should enable or avoid when it comes to a dd image that, presumably, must remain absolutely unchanged in order to ensure it can be recovered from?
For example, should solid compression be avoided? Is there a compression algorithm that's likely to compress dd images more efficiently (i.e. that offers the best trade-off between speed vs time) than any other? And so on.
Alternatively, are bit-wise images compressed in pretty much the same way as any other data would be? This is also a valid answer.
Here's what I have so far:
7z a -t7z -mx=9 -ms=on "SDcardbackup" "SDcardbackup.img"
compression 7-zip dd disk-image
asked Jan 24 at 1:33
HashimHashim
3,17163162
Often it's good to write zeros to unused sectors, so the image compresses better. Please read this answer.
– Kamil Maciorowski
Mar 6 at 17:58
add a comment |
I have a 30GB dd image of an SD card, and am using the 7-Zip command line to compress it. Are there any particular options I should enable or avoid when it comes to a dd image that, presumably, must remain absolutely unchanged in order to ensure it can be recovered from?
For example, should solid compression be avoided? Is there a compression algorithm that's likely to compress dd images more efficiently (i.e. that offers the best trade-off between speed vs time) than any other? And so on.
Alternatively, are bit-wise images compressed in pretty much the same way as any other data would be? This is also a valid answer.
Here's what I have so far:
7z a -t7z -mx=9 -ms=on "SDcardbackup" "SDcardbackup.img"
compression 7-zip dd disk-image
asked Jan 24 at 1:33
HashimHashim
3,17163162
I have a 30GB dd image of an SD card, and am using the 7-Zip command line to compress it. Are there any particular options I should enable or avoid when it comes to a dd image that, presumably, must remain absolutely unchanged in order to ensure it can be recovered from?
For example, should solid compression be avoided? Is there a compression algorithm that's likely to compress dd images more efficiently (i.e. that offers the best trade-off between speed vs time) than any other? And so on.
Alternatively, are bit-wise images compressed in pretty much the same way as any other data would be? This is also a valid answer.
Here's what I have so far:
7z a -t7z -mx=9 -ms=on "SDcardbackup" "SDcardbackup.img"
compression 7-zip dd disk-image
compression 7-zip dd disk-image
asked Jan 24 at 1:33
HashimHashim
3,17163162
asked Jan 24 at 1:33
HashimHashim
3,17163162
edited Jan 24 at 5:04
Hashim
asked Jan 24 at 1:33
HashimHashim
3,17163162
asked Jan 24 at 1:33
HashimHashim
3,17163162
asked Jan 24 at 1:33
HashimHashim
3,17163162
3,17163162
Often it's good to write zeros to unused sectors, so the image compresses better. Please read this answer.
– Kamil Maciorowski
Mar 6 at 17:58
add a comment |
Often it's good to write zeros to unused sectors, so the image compresses better. Please read this answer.
– Kamil Maciorowski
Mar 6 at 17:58
Often it's good to write zeros to unused sectors, so the image compresses better. Please read this answer.
– Kamil Maciorowski
Mar 6 at 17:58
Often it's good to write zeros to unused sectors, so the image compresses better. Please read this answer.
– Kamil Maciorowski
Mar 6 at 17:58
add a comment |
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Often it's good to write zeros to unused sectors, so the image compresses better. Please read this answer.
– Kamil Maciorowski
Mar 6 at 17:58