> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- > boun...@opensolaris.org] On Behalf Of Lanky Doodle > > Is there any argument against using the rpool for all data storage as well as > being the install volume?
Generally speaking, you can't do it. The rpool is only supported on mirrors, not raidz. I believe this is because you need rpool in order to load the kernel, and until the kernel is loaded, there's just no reasonable way to have a fully zfs-aware, supports-every-feature bootloader able to read rpool in order to fetch the kernel. Normally, you'll dedicate 2 disks to the OS, and then you build additional separate data pools. If you absolutely need all the disk space of the OS disks, then you partition the OS into a smaller section of the OS disks and assign the remaining space to some pool. But doing that partitioning scheme can be complex, and if you're not careful, risky. I don't advise it unless you truly have your back against a wall for more disk space. > Why does resilvering take so long in raidz anyway? There are some really long and sometimes complex threads in this mailing list discussing that. Fundamentally ... First of all, it's not always true. It depends on your usage behavior and the type of disks you're using. But the "typical" usage includes reading & writing a lot of files, essentially randomly over time, creating and deleting snapshots, using spindle disks, so the "typical" usage behavior does have a resilver performance problem. The root cause of the problem is that ZFS does not resilver the whole disk... It only resilvers the used portions of the disk. Sounds like a performance enhancer, right? It would be, if the disks were mostly empty ... or if ZFS were resilvering a partial disk, in order according to disk layout. Unfortunately, it's resilvering according to the temporal order blocks were written, and usually a disk is significantly full (say, 50% or more) and as such, the disks have to thrash all around, performing all sorts of random reads, until eventually it can read all the used parts in random order. It's worse on raidzN than on mirrors, because the number of items which must be read is higher in radizN, assuming you're using larger vdev's and therefore more items exist scattered about inside that vdev. You therefore have a higher number of things which must be randomly read before you reach completion. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
