> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- > boun...@opensolaris.org] On Behalf Of Gil Vidals > > What would the performance impact be of splitting up a 64 GB SSD into > four partitions of 16 GB each versus having the entire SSD dedicated to > each pool?
This is a common question, because people think, "I have 64G, but I can't possibly use more than 4G, so it's wasted space." True it's wasted space, but that's not what you should be thinking about. When you buy the SSD (or ddrdrive etc) for log device, the reason you're buying it is *not* for the sake of storage capacity. You're buying it for the sake of performance enhancement. The constrained resource is *not* usable capacity available. The constrained resource is bandwidth bottleneck to reach the device, and/or IOPS that the device is able to sustain. My advice is to forget about the wasted space, and just use the whole device as a log device for one pool. Otherwise, you'll be reducing the performance, and if you're going to do that, you're defeating the purpose of having the device. Depending on the size of the pool, you might even want more than one. Based on no particular numbers, I would say, one dedicated log device for every 10 spindle disks might be reasonable. Don't forget to mirror. Or at least think about it and make a conscious decision not to mirror. For the types of work that I do, an un-mirrored log device is an acceptable risk, but for some purposes, it wouldn't be. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
