On Wed, Apr 19, 2017 at 11:03 AM, 许雪寒 <xuxuehan@xxxxxx> wrote: > Thanks, everyone:-) > > I'm still not very clear. Do these cache "capabilities" only apply to metadata operations or both metadata and data? Both metadata and data are consistent between clients. If a client has the capability to buffer data for a file, it will be told to flush it before another client reads the file. Similarly, if a client has the capability to cache (for read) data for a file, it will be told to drop that before another client writes the file. Usually, if the MDS sees two clients using the same file concurrently, it will instruct both of them to switch to unbuffered IO. John > > -----邮件原件----- > 发件人: David Disseldorp [mailto:ddiss@xxxxxxx] > 发送时间: 2017年4月19日 16:46 > 收件人: 许雪寒 > 抄送: ceph-users@xxxxxxxxxxxxxx > 主题: Re: Does cephfs guarantee client cache consistency for file data? > > Hi, > > On Wed, 19 Apr 2017 08:19:50 +0000, 许雪寒 wrote: > >> I’m new to cephfs. I wonder whether cephfs guarantee client cache consistency for file content. For example, if client A read some data of file X, then client B modified the X’s content in the range that A read, will A be notified of the modification? > > Yes, clients are granted fine-grained cache "capabilities" by the MDS. > These capabilities can be revoked to trigger a flush of cached content, prior to satisfying a request from a separate client. > > Jeff Layton did a nice write up on this: > https://jtlayton.wordpress.com/2016/09/01/cephfs-and-the-nfsv4-change-attribute/ > > Cheers, David > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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