at Dezember, 17 2010, 17:48 <Lanky Doodle> wrote in [1]: > By single drive mirrors, I assume, in a 14 disk setup, you mean 7 > sets of 2 disk mirrors - I am thinking of traditional RAID1 here.
> Or do you mean 1 massive mirror with all 14 disks? Edward means a set of two-way-mirrors. Do you remember what he wrote: >> Also, in the event of a resilver, the 3x5 radiz will be faster. In rough >> numbers, suppose you have 1TB drives, 70% full. Then your resilver might be >> 8 days instead of 12 days. That's important when you consider the fact that >> during that window, you have degraded redundancy. Another failed disk in >> the same vdev would destroy the entire pool. > >> Also if a 2nd disk fails during resilver, it's more likely to be in the same >> vdev, if you have only 2 vdev's. Your odds are better with smaller vdev's, >> both because the resilver completes faster, and the probability of a 2nd >> failure in the same vdev is smaller. And this scene is a horrible notion. In that time resilvering is running you have to hope that nothing fails. In his example between 192 to 288 hours - thats a long a very long time. And be aware that a disk will broken at some point. > This is always a tough one for me. I too prefer RAID1 where > redundancy is king, but the trade off for me would be 5GB of > 'wasted' space - total of 7GB in mirror and 12GB in 3x RAIDZ. You lost at most space when you make a pool with mirrors BUT the I/O is much faster and its more secure and you have all the features of zfs too. http://blogs.sun.com/relling/entry/zfs_raid_recommendations_space_performance > Decisions, decisions..... My suggestion is make a two-way-mirror of small disks or ssd for the OS. This is not easy to do after installation, you have to look for a howto. Sorry I dont find the link at the moment. At Sol11 Express Oracle announced that at TestInstall you can set RootPool to mirror during installation. At the moment I try it out in a VM but I didnt find this option. :-( zpool create lankyserver mirror vdev1 vdev2 mirror vdev3 vdev4 When you need more space you can expand a bundle of two disks to your lankyserver. Each pair with the same capacity is effective. zpool add lankyserver mirror vdev5 vdev6 mirror vdev7 vdev8 ... Consider that its a good decision when you plan one spare disk. You can using the zpool add command when you want to add a spare disk at a later time. http://docs.sun.com/app/docs/doc/819-2240/zpool-1m?a=view When you build a raidz pool every disk in this pool must have the same space as the smallest disk have or bigger. Raidz pool uses only this space that the smallest disk have. The rest of the bigger disk is waste. At a mirrored pool only the pair must have the same space so you can use a pair of 1 TB disks, one pair of 2 TB disks at the same pool. In this scene your spare disk _must have_ the biggest space. Read this for your decision: http://constantin.glez.de/blog/2010/01/home-server-raid-greed-and-why-mirroring-still-best -- Best Regards Alexander Dezember, 17 2010 ........ [1] mid:382802084.111292604519623.javamail.tweb...@sf-app1 ........ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
