Hello, On Tue, 11 Oct 2016 01:07:16 +0000 Cory Hawkless wrote: > Thanks Jason, works perfectly. > > Do you know if ceph blocks the client IO until the journal has acknowledged it's write? I.E can I store my journal on slower disks or will that have a negative impact on performance? > Knowing nothing about this the little detail that it's a generic pool would suggest that all the usual rules and suspects apply. One assumes the RBD mirror needs to keep a crash safe state, so even if its writes were to be allowed to be asynchronous, how much of a backlog (and thus memory consumption) would be permissible? So my guess is that slow disks and journals would be a no-no. Let's see that Jason has to say. Christian > Is there perhaps a hole in the documentation here? I've not been able to find anything in the man page for RBD nor on the Ceph website? > > Regards, > Cory > > > -----Original Message----- > From: Jason Dillaman [mailto:jdillama@xxxxxxxxxx] > Sent: Tuesday, 11 October 2016 7:57 AM > To: Cory Hawkless <Cory@xxxxxxxxxxxxxx> > Cc: ceph-users@xxxxxxxxxxxxxx > Subject: Re: RBD-Mirror - Journal location > > Yes, the "journal_data" objects can be stored in a separate pool from the image. The rbd CLI allows you to use the "--journal-pool" argument when creating, copying, cloning, or importing and image with journaling enabled. You can also specify the journal data pool when dynamically enabling the journaling feature using the same argument. > Finally, there is a Ceph config setting of "rbd journal pool = XYZ" > that allows you to default new journals to a specific pool. > > Jason > > On Mon, Oct 10, 2016 at 1:59 AM, Cory Hawkless <Cory@xxxxxxxxxxxxxx> wrote: > > I’ve enabled RBD mirroring on my test clusters and it seems to be > > working well, my question is ‘Can we store the RBD mirror journal on a > > different pool?’ > > > > > > > > Currently when I do something like rados ls –p sas I see > > > > > > > > > > > > rbd_data.a67d02eb141f2.0000000000000bd1 > > > > rbd_data.a67d02eb141f2.0000000000000b73 > > > > rbd_data.a67d02eb141f2.000000000000036d > > > > rbd_data.a67d02eb141f2.000000000000074e > > > > journal_data.75.a67d02eb141f2.175 > > > > rbd_data.a67d02eb141f2.0000000000000bb6 > > > > rbd_data.a67d02eb141f2.0000000000000bae > > > > rbd_data.a67d02eb141f2.0000000000000313 > > > > rbd_data.a67d02eb141f2.0000000000000bb3 > > > > > > > > > > > > Depending on how far behind the remote cluster is on sync, there are > > more or less of the journal entries. > > > > > > > > I am worried about the overhead of storing the journal on the same set > > of disks as the actual RBD images. > > > > My understanding is that enabling journaling is going to double the > > IOPS on the disks, is that correct? > > > > > > > > Any assistance appreciated > > > > > > > > Regards, > > > > Cory > > > > > > > > > > _______________________________________________ > > ceph-users mailing list > > ceph-users@xxxxxxxxxxxxxx > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > > > > -- > Jason > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com -- Christian Balzer Network/Systems Engineer chibi@xxxxxxx Global OnLine Japan/Rakuten Communications http://www.gol.com/ _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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