Hi, Obviously it depends on the number of inodes (files,dirs etc) you have. However, if the zfs pool uses ashift=12, which will be the default for most SSDs and large HDDs, it can have quite an overhead for MDTs. It takes a lot of bandwidth on MDTs if you do a lot of metedata operations.
You can check it by running 'zdb |grep ashift'. We are using ashift=9 on SSDs for this reason, even though the SDDs would prefer it differently. Cheers, Hans Henrik On 27.01.2020 19.07, Nehring, Shane R [LAS] wrote: > Hey all, > > We've been running a lustre volume for a few years now and it's been > working quite well. We've been using ZFS as the backend storage and > while that's been working well I've noticed that the space usage is > a little weird on the mdt: > > NAME PROPERTY VALUE SOURCE > store/work-mdt used 4.91T - > store/work-mdt logicalused 960G - > store/work-mdt referenced 4.91T - > store/work-mdt logicalreferenced 960G - > store/work-mdt compressratio 1.00x - > > Just wondering if anyone else has noticed this kind of overhead. > > > _______________________________________________ > lustre-discuss mailing list > [email protected] > http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org > _______________________________________________ lustre-discuss mailing list [email protected] http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org
