[lustre-discuss] max_frags incompatible

[Makia Minich]

Recently we upgraded our lustre servers to RHEL 8 with lustre 2.15.5 but due to scheduling the clients are still currently at RHEL 7 with lustre version 2.12.6. Infiniband is the interconnect.

We've found that the client will fail to mount unless we run a "lnetctl ping" from the server side to the client. Once that happens then the client will ultimately mount. We've seen the following error in the logs on the server side:

lNet: 1920125:0:(o2iblnd_cd.c:2587:kiblnd_passive_connect()) Can’t accept conn from 172.16.19.6 at o2ib (version 12): max_frags 256 incompatible without FMR_pool (257 wanted)

Attempting to set map_on_demand on the client side didn't help, resulting in the same error. Are there any parameters or configuration changes that may help the situation? At this time we aren't able to upgrade the client side to RHEL 8, so we're ultimately limited on available versions, so looking for ideas on what to try next.

Thanks.
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