Re: How to calculate used rate of a OST ?

On Apr 18, 2007  16:19 +0800, swin wang wrote:
>    We hope that if an OST's used rate up to 90% or 95%, it can be marked
> FULL, and avoid to use this OST. we plan to add a state FULL in structure
> lov_tgt_desc, when the
> OST  used  rate up to  90% or 95%, set its state to FULL, and when create
> new object,
> don't use these FULL OST.
>    We want to know how to calculate used rate of a  OST,  is it like this:
>        used rate = lov->lov_tgts[i]->ltd_exp->exp_obd->obd_osfs.os_bavail /
> ov->lov_tgts[i]->ltd_exp->exp_obd->obd_osfs.os_blocks  ??

This is already done on the OSTs in filter_precreate(), though the limit is
only 0.1%.  I'd be happy to accept a patch which made this limit a tunable
in /proc that can be set by the sysadmin.

There is also in 1.6 (and betas) some free space management that is tunable
on the MDS /proc/fs/lustre/lov/*/qos_priofree which is a percentage of
weight which you want to give to "free" OSTs.  In your case you want this
to be relatively high (90% is the default in later betas).  If this is not
sufficient to have the MDS allocate very preferentially on free OSTs, please
provide more details on your configuration.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.