Re: Image Catalog over NFS

Hello,

Am 20.12.2020 um 17:22 schrieb Patrik Schindler <poc@xxxxxxxxxx>:

I wonder if one can save time and unnecessary network traffic by not writing a file full of zeros, but create a sparse file. Instead of

dd if=/dev/zero of=IMAGE01.ISO bs=1M count=10000

do a

dd if=/dev/zero of=IMAGE01.ISO bs=1M seek=10000 count=0

See https://en.wikipedia.org/wiki/Sparse_file for details.

I did not test if IBM i can cope with sparse files, but I don’t see any reason why it shouldn’t.

Today I finally managed to get image catalogs for save/restore to eventually work on a 7.3 machine.

Using sparse files works like a charm. No needless I/O on the NFS server for allocating Gigabytes of zeros. No extra space being consumed because of needless zeros.

Alternate command to create such an empty file:

truncate -s 30G backup.udf

echo "backup.udf W" > VOLUME_LIST

The "W" is important. Without it, the image catalog will be read-only.

For me, I stick to the already established ftp workflow. The backup server uses jumbo frames, while the E4A isn’t configured for them. So, UDP (NFS) answer packets will be lost in transit and NFS doesn’t work. Mount and un mount work, though.

This is what I've forgotten and rediscovered today. I hereby thank my older self for his help to solve this mystery. ;-)

I did not try if NFS can be forced over TCP in IBM i.

According to the documentation, it's not possible.

In 7.3, the service tools adapter MTU cannot be configured.

No easy way out here.

:wq! PoC