Torrents are divided into pieces, which are then shuffled around by Bittorrent clients. The more pieces, the more overhead there is for controlling which client has which piece. On the other hand, if the piece size is too big, it may take the clients a bit longer to get their first full piece, which they could then send to other clients in exchange for new pieces.<br />
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The opinion is divided on the correct piece size, but in any case I suppose the piece size could be made somewhat bigger than what it is now. This would also make the torrent files smaller, although this is likely less of a concern to anyone nowadays.<br />
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Here's a summary of the CentOS torrents I have:<br />
<br />
[anssi@norsu centos]$ for i in *.torrent; do transmission-show $i | egrep -e " (Piece Size|Name):"; done | awk '{if (NR%2) {prev=$0} else {print prev,$0}}' | sort<br />
Name: CentOS-4.8-i386-bin1to4 Piece Size: 256.0 KiB<br />
Name: CentOS-4.8-i386-binDVD Piece Size: 256.0 KiB<br />
Name: CentOS-4.8-x86_64-bin1to5 Piece Size: 256.0 KiB<br />
Name: CentOS-4.8-x86_64-binDVD Piece Size: 256.0 KiB<br />
Name: CentOS-5.6-i386-bin-1to7 Piece Size: 256.0 KiB<br />
Name: CentOS-5.6-i386-bin-DVD Piece Size: 256.0 KiB<br />
Name: CentOS-5.6-i386-LiveCD Piece Size: 256.0 KiB<br />
Name: CentOS-5.6-x86_64-bin-1to8 Piece Size: 256.0 KiB<br />
Name: CentOS-5.6-x86_64-bin-DVD Piece Size: 256.0 KiB<br />
Name: CentOS-5.6-x86_64-LiveCD Piece Size: 256.0 KiB<br />
Name: CentOS-5.7-i386-bin-1to8 Piece Size: 256.0 KiB<br />
Name: CentOS-5.7-i386-bin-DVD Piece Size: 256.0 KiB<br />
Name: CentOS-5.7-x86_64-bin-1to8 Piece Size: 256.0 KiB<br />
Name: CentOS-5.7-x86_64-bin-DVD Piece Size: 256.0 KiB<br />
Name: CentOS-5.8-i386-bin-1to7 Piece Size: 256.0 KiB<br />
Name: CentOS-5.8-i386-bin-DVD Piece Size: 256.0 KiB<br />
Name: CentOS-5.8-x86_64-bin-1to8 Piece Size: 256.0 KiB<br />
Name: CentOS-5.8-x86_64-bin-DVD Piece Size: 256.0 KiB<br />
Name: CentOS-6.0-i386-bin-DVD Piece Size: 256.0 KiB<br />
Name: CentOS-6.0-i386-LiveCD Piece Size: 256.0 KiB<br />
Name: CentOS-6.0-i386-LiveDVD Piece Size: 256.0 KiB<br />
Name: CentOS-6.0-x86_64-bin-DVD Piece Size: 256.0 KiB<br />
Name: CentOS-6.0-x86_64-LiveCD Piece Size: 256.0 KiB<br />
Name: CentOS-6.0-x86_64-LiveDVD Piece Size: 256.0 KiB<br />
Name: CentOS-6.1-i386-bin-DVD1to2 Piece Size: 256.0 KiB<br />
Name: CentOS-6.1-i386-LiveCD Piece Size: 256.0 KiB<br />
Name: CentOS-6.1-i386-LiveDVD Piece Size: 256.0 KiB<br />
Name: CentOS-6.1-x86_64-bin-DVD1to2 Piece Size: 256.0 KiB<br />
Name: CentOS-6.1-x86_64-LiveCD Piece Size: 256.0 KiB<br />
Name: CentOS-6.1-x86_64-LiveDVD Piece Size: 256.0 KiB<br />
Name: CentOS-6.2-i386-bin-DVD1to2 Piece Size: 256.0 KiB<br />
Name: CentOS-6.2-i386-LiveCD Piece Size: 256.0 KiB<br />
Name: CentOS-6.2-i386-LiveDVD Piece Size: 256.0 KiB<br />
Name: CentOS-6.2-x86_64-bin-DVD1to2 Piece Size: 256.0 KiB<br />
Name: CentOS-6.2-x86_64-LiveCD Piece Size: 256.0 KiB<br />
Name: CentOS-6.2-x86_64-LiveDVD Piece Size: 256.0 KiB<br />
Name: CentOS-6.3-i386-bin-DVD1to2 Piece Size: 512.0 KiB<br />
Name: CentOS-6.3-i386-LiveCD Piece Size: 64.00 KiB<br />
Name: CentOS-6.3-i386-LiveDVD Piece Size: 128.0 KiB<br />
Name: CentOS-6.3-x86_64-bin-DVD1to2 Piece Size: 512.0 KiB<br />
Name: CentOS-6.3-x86_64-LiveCD Piece Size: 64.00 KiB<br />
Name: CentOS-6.3-x86_64-LiveDVD Piece Size: 128.0 KiB<br />
<br />
It looks like some other method was used for creating the C6.3 torrents than before. Bug 5926 also suggests that some other method was used for the 6.3 torrents. I don't know if that was a one-time occurrence or if all the future torrents will be made using the same method as the C6.3 torrents.<br />
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I would suggest using a 1MB piece size for DVD images (and complete 1-8 CD sets for C5.x) and a 512KB piece size for smaller files. If for some reason only one piece size can be used for all torrents, 512KB would be fine.
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