While in theory this should be true, I'm not finding it to be the case for a typical enterprise LSI card with 24 drives attached. We tried a variety of ratios and went back to collocated journals on the spinning drives.
Eagerly awaiting the tiered performance changes to implement a faster tier via SSD. -- Warren Journal on SSD should effectively double your throughput because data will not be written to the same device twice to ensure transactional integrity. Additionally, by placing the OSD journal on an SSD you should see less latency, the disk head no longer has to seek back and forth between the journal and data partitions. For large writes it's not as critical to have a device that supports high IOPs or throughput because large writes are striped across many 4MB rados objects, relatively evenly distributed across the cluster. Small write operations will benefit the most from an OSD data partition with a writeback cache like btier/flashcache because it can absorbs an order of magnitude more IOPs and allow a slower spinning device catch up when there is less activity.
|
_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
