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2003
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If anyone has any explanation, why `dakol` is 20x faster than the other computers, please write it here. Is it because of the position of the disk partition, or that it's larger? `pc232` is full, but the other computers have around the same disk usage. Note: `/var` and `/tmp` is on the same partition on all computers. | Note 1: XFS filesystem was created using mkfs.xfs, ext3 filesystem was created with mkfs.ext3. No options added. |
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Update: I also tried on `august` to copy the `base.cow` to a larger 233GB partition, 0.2% full, and then copy on this partition, and it took 6s. So a little improvement, but that is not the reason, why it is so terribly slow, compared to `dakol`. | Note 2: On `dakol` with XFS filesystem, cp takes 0.5s, `sudo sync` takes 3s (!), rm takes 0.5s, and another `sudo sync` takes 2.8s. However, with ext3 filesystem, the `sudo sync` is negligible. |
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The only explanation I can think of is that `xfs` filesystem is 64bit, and thus is simply 20x faster on amd64 debian, compared to i386 debian... | |
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Update: I think I know: on `dakol`, cp takes 0.5s, `sudo sync` takes 3s (!), rm takes 0.5s, and another `sudo sync` takes 2.8s. So it's only 2x faster than `august`. And that could be explained by the 64bits. However, in practice, since the kernel is caching the files, it's 20x faster. Solution: So I know where the problem is. I just used an empty 10GB partition on pc232. |
Conclusion: The ext3 filesystem is truly superior to XFS for the `cowbuilder` purpose. Just use it and you'll be fine. |
Note: please don't edit the page, I found the solution, polishing this page at this very moment.
Benchmarks of COW directory copies and removal in [:cowbuilder: cowbuilder].
Details
The numbers in the copy column were generated using:
time sudo cp -al /var/cache/pbuilder/base.cow /tmp/new
and in the remove column:
time sudo rm -rf /tmp/new
Everything is in seconds. XFS filesystems:
computer |
copy |
remove |
computer details |
pc232 |
16.1 |
18.2 |
Intel Core 2 Duo, ST3250820AS /dev/sda1 (10GB, xfs, 80% full), sid, i386 |
pc232 |
9.0 |
10.0 |
Intel Core 2 Duo, ST3250820AS /dev/sda2 (10GB, xfs, 2.4% full), sid, i386 |
august |
9.3 |
10.9 |
Intel Core 2 Quad, ST3320620AS /dev/sda1 (20GB, xfs, 20% full), sid, i386 |
august |
5.8 |
9.5 |
Intel Core 2 Quad, ST3320620AS /dev/sda3 (233GB, xfs, 0.2% full), sid, i386 |
dakol |
0.48 |
0.5 |
AMD Athlon 64 3800+, ST3160827AS /dev/sda7 (135GB, xfs, 32% full), sid, amd64 |
fuji |
13.9 |
16.4 |
Intel Core Duo, WDC WD1600BEVS-2 /dev/sda1 (14GB, xfs, 33% full), sid, i386 |
Ext3 filesystems:
computer |
copy |
remove |
computer details |
pc232 |
0.2 |
0.14 |
Intel Core 2 Duo, ST3250820AS /dev/sda2 (10GB, ext3, 2.4% full), sid, i386 |
august |
0.22 |
0.13 |
Intel Core 2 Quad, ST3320620AS /dev/sda5 (42GB, ext3, 0.9% full), sid, i386 |
dakol |
0.22 |
0.15 |
AMD Athlon 64 3800+, ST3160827AS /dev/sda5 (2GB, ext3, 14.5% full), sid, amd64 |
Note 1: XFS filesystem was created using mkfs.xfs, ext3 filesystem was created with mkfs.ext3. No options added.
Note 2: On dakol with XFS filesystem, cp takes 0.5s, sudo sync takes 3s (!), rm takes 0.5s, and another sudo sync takes 2.8s. However, with ext3 filesystem, the sudo sync is negligible.
Conclusion: The ext3 filesystem is truly superior to XFS for the cowbuilder purpose. Just use it and you'll be fine.