Hi, I have been doing some testing with striped rbd images and have a question about the calculation of the optimal_io_size and minimum_io_size parameters. My test image was created using a 4M object size, stripe unit 64k and stripe count 16.
In the kernel rbd_init_disk() code: unsigned int objset_bytes = rbd_dev->layout.object_size * rbd_dev->layout.stripe_count; blk_queue_io_min(q, objset_bytes); blk_queue_io_opt(q, objset_bytes); Which resulted in 64M minimal / optimal io sizes. If I understand the meaning correctly then even for a small write there is going to be at least 64M data written? My use case is a ceph cluster (13.2.4) hosting rbd images for VMs running on Xen. The rbd volumes are mapped to dom0 and then passed through to the guest using standard blkback/blkfront drivers. I am doing a bit of testing with different stripe unit sizes but keeping object size * count = 4M. Does anyone have any experience finding optimal rbd parameters for this scenario? Thanks, James Zynstra is a private limited company registered in England and Wales (registered number 07864369). Our registered office and Headquarters are at The Innovation Centre, Broad Quay, Bath, BA1 1UD. This email, its contents and any attachments are confidential. If you have received this message in error please delete it from your system and advise the sender immediately. _______________________________________________ ceph-users mailing list firstname.lastname@example.org http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com