Sorry for the finger slip; I do not like MS products!
In formatting a 3390 eckd image, it is clearly better
to use 4096 than 1024 byte blocks!
I formatted two 3390-3 volumes, one with 1K blocks and
one with 4K blocks. I then put ext2 filesystems of 1k
and 4bk blocks respectively. (SuSE SLES8 SP3)
Using files from 0 bytes to 1024 bytes, I could get
1.2GB and 300,947 files on the 4k block but I could
only get .812 GB and 206,741 files on the 1k blocks!
Since I used from 0 to 1024byte files, all "small", 4k
blocks still got more and files on the back. If I had
used even bigger files, I would infer that 4k blocks
would look even better.
Here is a side by side comparison:
1k cdl 4k cdl
fmt -b 1024 -b 4096
ext2 -b 1024 -b 4096
blocks 1,626,740 2,366,164
empty 1.6 gb 2.3GB
"full" 0.812 GB 1.2 GB
files 206,741 300,947
The file systems gave out before all the space was
used - each filesystem showed 54% used, but you could
not allocate any new files.
The difference is space usage is because, with blocks
greater than 4096 on a 3390 eckd, more "room" on the
disk image is taken up with eckd overhead than data.
For blocks gt that about 4096, there is more data on
the track than overhead.
=====
Jim Sibley
RHCT, Implementor of Linux on zSeries
"Computer are useless.They can only give answers." Pablo Picasso
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