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0710326ac5
This is an extensible version of 'mkfs' which supports optional arguments. There is now no need for 'mkfs_b' since you should use 'mkfs_opts' with the optional 'blocksize' argument instead.
71 lines
2.4 KiB
Plaintext
71 lines
2.4 KiB
Plaintext
This directory contains some experimental work for capturing traces of
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block device operations while filesystem operations are performed.
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You can trace any operation that libguestfs supports, including
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partitioning, mkfs, LVM operations, and filesystem operations. You
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can enable and disable tracing in order to capture single operations
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such as a single write, or groups of operations. You can examine the
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traces by hand (as text files) or turn them into graphical
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visualizations.
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IMPORTANT NOTE: This is not upstream (in qemu) nor integrated into
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libguestfs. We should probably be using the 'blktrace' command
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instead, or if that is not suitable, get a more reliable and useful
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trace mechanism added to qemu (the current patch is not suitable for
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upstreaming).
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The *.qtr files are qemu trace files, produced using the unofficial
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qemu patch in the current directory.
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- guestfish-N-fs-10M.qtr
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The command 'guestfish -N fs:ext2:10M' before we modified the
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part-disk API to align the partition to 64 sectors.
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- guestfish-N-fs-10M-aligned-part-disk.qtr
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The command 'guestfish -N fs:ext2:10M' after we modified the
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part-disk API to align the partition to 64 sectors.
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- guestfish-add-mount.qtr
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$ guestfish -a test1.img -m /dev/sda1
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where test1.img was created by the previous command.
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- guestfish-write-hello.qtr
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$ guestfish -a test1.img -m /dev/sda1 \
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debug qtrace "/dev/vda on" : \
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write /hello "hello, world." : \
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debug qtrace "/dev/vda off"
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where test1.img was created by the command above.
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This is just the creation of a new file with a small amount of content.
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Within this trace file, the qtrace on/off commands appear as patterns
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of reads. For on: 2, 21, 15, 2. For off: 2, 15, 21, 2.
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- guestfish-lv-ext4-4k.qtr
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$ guestfish \
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alloc test1.img 40M : \
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run : \
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part-disk /dev/vda mbr : \
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pvcreate /dev/vda : \
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vgcreate VG /dev/vda : \
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lvcreate LV VG 32 : \
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mkfs-opts ext4 /dev/VG/LV blocksize:4096
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Some points to note:
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* an ext4 filesystem, so it has a journal and extents
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* 4K block size, so we expect writes to be aligned
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* located inside an LV, so more realistic
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- guestfish-lv-ext4-4k-write-hello.qtr
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$ guestfish -a test1.img -m /dev/VG/LV \
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debug qtrace "/dev/vda on" : \
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write /hello "hello, world." : \
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debug qtrace "/dev/vda off"
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where test1.img was created by the previous command.
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