Nah, I would use one Filesystem unless you can’t. The backtrace does create another object but IIRC it’s a maximum one IO per create/rename (on the file). On Wed, Jun 13, 2018 at 1:12 PM Webert de Souza Lima <webert.b...@gmail.com> wrote:
> Thanks for clarifying that, Gregory. > > As said before, we use the file layout to resolve the difference of > workloads in those 2 different directories in cephfs. > Would you recommend using 2 filesystems instead? By doing so, each fs > would have it's default data pool accordingly. > > > Regards, > > Webert Lima > DevOps Engineer at MAV Tecnologia > *Belo Horizonte - Brasil* > *IRC NICK - WebertRLZ* > > > On Wed, Jun 13, 2018 at 11:33 AM Gregory Farnum <gfar...@redhat.com> > wrote: > >> The backtrace object Zheng referred to is used only for resolving hard >> links or in disaster recovery scenarios. If the default data pool isn’t >> available you would stack up pending RADOS writes inside of your mds but >> the rest of the system would continue unless you manage to run the mds out >> of memory. >> -Greg >> On Wed, Jun 13, 2018 at 9:25 AM Webert de Souza Lima < >> webert.b...@gmail.com> wrote: >> >>> Thank you Zheng. >>> >>> Does that mean that, when using such feature, our data integrity relies >>> now on both data pools' integrity/availability? >>> >>> We currently use such feature in production for dovecot's index files, >>> so we could store this directory on a pool of SSDs only. The main data pool >>> is made of HDDs and stores the email files themselves. >>> >>> There ain't too many files created, it's just a few files per email >>> user, and basically one directory per user's mailbox. >>> Each mailbox has a index file that is updated upon every new email >>> received or moved, deleted, read, etc. >>> >>> I think in this scenario the overhead may be acceptable for us. >>> >>> >>> Regards, >>> >>> Webert Lima >>> DevOps Engineer at MAV Tecnologia >>> *Belo Horizonte - Brasil* >>> *IRC NICK - WebertRLZ* >>> >>> >>> On Wed, Jun 13, 2018 at 9:51 AM Yan, Zheng <uker...@gmail.com> wrote: >>> >>>> On Wed, Jun 13, 2018 at 3:34 AM Webert de Souza Lima >>>> <webert.b...@gmail.com> wrote: >>>> > >>>> > hello, >>>> > >>>> > is there any performance impact on cephfs for using file layouts to >>>> bind a specific directory in cephfs to a given pool? Of course, such pool >>>> is not the default data pool for this cephfs. >>>> > >>>> >>>> For each file, no matter which pool file data are stored, mds alway >>>> create an object in the default data pool. The object in default data >>>> pool is used for storing backtrace. So files stored in non-default >>>> pool have extra overhead on file creation. For large file, the >>>> overhead can be neglect. But for lots of small files, the overhead may >>>> affect performance. >>>> >>>> >>>> > Regards, >>>> > >>>> > Webert Lima >>>> > DevOps Engineer at MAV Tecnologia >>>> > Belo Horizonte - Brasil >>>> > IRC NICK - WebertRLZ >>>> > _______________________________________________ >>>> > ceph-users mailing list >>>> > ceph-users@lists.ceph.com >>>> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>>> >>> _______________________________________________ >>> ceph-users mailing list >>> ceph-users@lists.ceph.com >>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>> >>
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