On 9/24/11 11:31 AM, Ted Ts'o wrote: > On Fri, Sep 23, 2011 at 05:51:24PM -0300, Carlos Maiolino wrote: >> On Fri, Sep 23, 2011 at 02:24:23PM -0600, Andreas Dilger wrote: >>> On 2011-09-23, at 12:47 PM, Carlos Maiolino wrote: >>>> The current example in the man page uses bzip2 to compress >>>> the raw image file created by the e2image, but, bzip2 does >>>> not honors sparse files, which causes the image to have the >>>> same size of the filesystem. >>>> Using tar together with bzip2 will make the compressed file >>>> to honor the sparsed file, which makes it more transportable >>>> than the current one if the filesystem is large. > > The problem with using tar is that it requires extra disk space by the > user --- somewhere a bit more than double the extra disk space > (because you need to have space for the hda1.e2i file before it gets > compressed). For very large file systems, this can be quite > significant. My general philosophy has been to make things easy as > possible for the users as being more important for the developers. > > For the developers, we do have contrib/make-sparse.c. All we have to do is: > > bunzip2 < hda1.e2i.bz2 | make-sparse hda1.e2i > > ... and this creates a sparse file in hda1.e2i. or | cp --sparse=always /dev/stdin sparse.img works too. But have you ever tried this with a multi-terabyte image? It takes -forever- to process all those 0s, with cpus pegged. The tar command seems to actually annotate the sparseness efficiently. Ted, your concern about space - it doesn't take the full fs size worth of space, right, just the metadata space? So in general it should not be THAT much ... -Eric >>> Even better would be the use of the QCOW2 format that Lukas added, >>> if it could also be operated on directly by the e2fsprogs utils (I >>> don't know if that is possible or not). >>> >> The QCOW2 format can only be operated with qcow2 capable tools like >>> qemu-img to use directly with e2fsprogs tools, we still need to >>> use raw images. > > Yeah, it would be nice if we had an io_manager implementation that > understood qcow2, which could then be used by dumpe2fs and debugfs. > Hopefully at some point someone will implement it. > > - Ted > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
