[lustre-discuss] Additional dataset for Lustre OST with ZFS backend

Tung-Han Hsieh thhsieh at twcp1.phys.ntu.edu.tw
Sun Aug 9 03:19:35 PDT 2020

Dear All,

We have a lustre file system version 2.10.7. Its layout is the following:

1. MGS+MDT (ldiskfs): chome-MDT0000:  /dev/sda7
2. OST (ZFS):         chome-OST0004:  chome_ost/ost (41% occupied)

They are located in different machines. Now due to some problem of the
existing lustre system which we may eventually have no solution to fix,
we have to plan to create another new Lustre file system and move data
from the old one to the new one.

Now it is easy to find other machine / partiton for new MGS+MDT, but
it is difficult to find a large enough disk array for new OST. Since
currently the existing OST chome-OST0004 lives in a ZFS which is not
fully occupied, and we know that ZFS can have multiple datasets. So
is it possible to create a new data set in the same device for the
new OST belonging to the new Lustre file system ? e.g.:

	chome_ost/ost2 (new OST for new Lustre file system)

Then we can set quota for the old OST, mount the old and new Lustre
file system, and transfer all user data from the old one to the new
one. We would like to knwo whether this is possible, and how to do

Thank you very much.


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