Re: TCT / tctutils for HP-UX 11.00 + some insight into unrm'ing large files

From: Salvador Mandujano Vergara (782502-6) (smvat_private)
Date: Thu Aug 08 2002 - 05:56:39 PDT

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    >My measuements are based on FreeBSD version 4.4 (perhaps 4.3), a
>4.4BSD descendant which creates cylinder groups of 32768 blocks
>(32MB) by default. FFS has evolved since the papers from the
>eighties.

Something very very similar happens with Suse 7.3 (Iīm quite surprised). 
The OS is allocating more than 16MB in every group. Iīll try to perform a 
similar test and will post my results. Certainly the icat info.you got is 
interesting. Iīm also working with fsī FreeBSD and didnīt know thatīs the 
way it works.

- Salvador Mandujano

>
>I just repeated the experiment, on a not quite virgin disk, with
>a 240MB file. It shows that FreeBSD allocate 16MB in every cylinder
>group. The first run of indirect blocks is broken up probably
>because of other files. The other runs of indirect blocks are
>pretty consistent and span about 17392 blocks each.
>
>Below is icat -v output, which shows the block numbers for inode,
>indirect and data blocks.
>
>	Wietse
>
>fs_read_block: read block 262176 offs 268468224 len 8192 (inode block)
>fs_read_block: read block 17025112 offs 17433714688 len 8192 (data block)
>....
>fs_read_block: read block 17025200 offs 17433804800 len 8192 (data block)
>
>fs_copy_indir: level 1 block 4444896
>fs_read_block: read block 4444896 offs 4551573504 len 8192 (disk address 
block)
>fs_read_block: read block 17025208 offs 17433812992 len 8192 (data block)
>....
>fs_read_block: read block 17058992 offs 17468407808 len 8192 (data block)
>
>fs_copy_indir: level 2 block 30244872
>fs_read_block: read block 30244872 offs 30970748928 len 8192 (disk 
address block)
>
>fs_copy_indir: level 1 block 30245888
>fs_read_block: read block 30245888 offs 30971789312 len 8192 (disk 
address block)
>fs_read_block: read block 30245896 offs 30971797504 len 8192 (data block)
>....
>fs_read_block: read block 30262272 offs 30988566528 len 8192 (data block)
>
>fs_copy_indir: level 1 block 30277640
>fs_read_block: read block 30277640 offs 31004303360 len 8192 (disk 
address block)
>....
>fs_read_block: read block 30295032 offs 31022112768 len 8192 (data block)
>fs_copy_indir: level 1 block 30310408
>fs_read_block: read block 30310408 offs 31037857792 len 8192 (disk 
address block)
>....
>fs_read_block: read block 30327800 offs 31055667200 len 8192 (data block)
>
>fs_copy_indir: level 1 block 30343176
>fs_read_block: read block 30343176 offs 31071412224 len 8192 (disk 
address block)
>....
>fs_read_block: read block 30360568 offs 31089221632 len 8192 (data block)
>
>fs_copy_indir: level 1 block 30375944
>fs_read_block: read block 30375944 offs 31104966656 len 8192 (disk 
address block)
>
>	Wietse
>
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