Thanks for your reply Andreas. I have one more question regarding the size of the reserved space. Our average file size is 1MB, OST size is 7.2TB and I am planning to set reserved space to 0.15% which will give us 12GB per OST. Would you agree that this is enough to keep fragmentation low?
Best regards, Wojciech On 25 November 2010 23:57, Andreas Dilger <[email protected]> wrote: > On 2010-11-25, at 13:12, Wojciech Turek wrote: > > I forgot to ask, is setting reserved % to 0 is safe on Lustre > filesysytem? > > It is safe, but can lead to serious (and permanent) fragmentation of the > filesystem, which can lead to permanent performance loss. Consider reducing > it to some smaller fraction than 5%, but leaving some reserve. > > > On 25 November 2010 19:15, Wojciech Turek <[email protected]> wrote: > >> I am trying to reclaim the default 5% of reserved disk space on Lustre > filesystem following procedure describe in the Lustre manual (chapter > 23.3.10). File system is in use and I would like to avoid any downtime. > >> > >> [r...@oss17 ~]# tune2fs -m 1 /dev/sdg > >> tune2fs 1.41.12.2.ora1 (14-Aug-2010) > >> tune2fs: MMP: device currently active while trying to open /dev/sdg > >> > >> I understand it is the MMP flag which prevent tune2fs to access the > device, is there a way to work around this or is my only option to umount > OSTs (eek, downtime) > > It should be possible to do this with a modification to tune2fs. > > The issue is that this operation is only safe on a mounted filesystem if it > is a local mount, and not a remote mount. tune2fs probably needs to skip > the MMP checking in this case, but it needs to check that the filesystem is > mounted locally. > > Cheers, Andreas > -- > Andreas Dilger > Lustre Technical Lead > Oracle Corporation Canada Inc. > >
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