On 9/26/11 7:22 AM, Bernd Schubert wrote: > On 09/24/2011 06:31 PM, 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. > > The problem is that the bzip2 run will take a huge amount of time to > compress all the zeros. In 2009 (with a recent CPU of that time) I > aborted such a run for a 8TiB file system after a couple of days, > then stored the e2image directly on disk and compressed it with tar > and sparse support, which finished after only 12 hours... I don't > think more modern CPUs are much faster for single threaded runs as > bzip2 does it. So IMHO the man page should at least warn about that > issue and suggest to use a similar tar command. Agreed! I think they both have their place. passing images around in qcow format may be best in the long run though. -Eric > > Cheers, > Bernd > -- > 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
