Hi, > Now that zfsboot is becoming available, I'm wondering how to put it to > use. Imagine a system with 4 identical disks. Of course I'd like to use
you lucky one :). > raidz, but zfsboot doesn't do raidz. What if I were to partition the > drives, such that I have 4 small partitions that make up a zfsboot > partition (4 way mirror), and the remainder of each drive becomes part > of a raidz? Sounds good. Performance will suffer a bit, as ZFS thinks it has two pools with 4 spindels each, but it should still perform better than the same on a UFS basis. You may also want to have two 2-way mirrors and keep the second for other purposes such as a scratch space for zfs migration or as spare disks for other stuff. > Do I still have the advantages of having the whole disk > 'owned' by zfs, even though it's split into two parts? I'm pretty sure that this is not the case: - ZFS has no guarantee that someone will do something else with that other partition, so it can't assume the right to turn on disk cache for the whole disk. - Yes, it could be smart and realize that it does have the whole disk, only split up across two pools, but then I assume that this is not your typical enterprise class configuration and so it probably didn't get implemented that way. I'd say that not being able to benefit from the disk drive's cache is not as bad in the face of ZFS' other advantages, so you can probably live with that. > Swap would probably have to go on a zvol - would that be best placed on > the n-way mirror, or on the raidz? I'd place it onto the mirror for performance reasons. Also, it feels cleaner to have all your OS stuff on one pool and all your user/app/data stuff on another. This is also recommended by the ZFS Best Practices Wiki on www.solarisinternals.com. Now back to the 4 disk RAID-Z: Does it have to be RAID-Z? Maybe you might want to reconsider using 2 2-way mirrors: - RAID-Z is slow when writing, you basically get only one disk's bandwidth. (Yes, with variable block sizes this might be slightly better...) - RAID-Z is _very_ slow when one disk is broken. - Using mirrors is more convenient for growing the pool: You run out of space, you add two disks, and get better performance too. No need to buy 4 extra disks for another RAID-Z set. - When using disks, you need to consider availability, performance and space. Of all the three, space is the cheapest. Therefore it's best to sacrifice space and you'll get better availability and better performance. Hope this helps, Constantin -- Constantin Gonzalez Sun Microsystems GmbH, Germany Platform Technology Group, Global Systems Engineering http://www.sun.de/ Tel.: +49 89/4 60 08-25 91 http://blogs.sun.com/constantin/ Sitz d. Ges.: Sun Microsystems GmbH, Sonnenallee 1, 85551 Kirchheim-Heimstetten Amtsgericht Muenchen: HRB 161028 Geschaeftsfuehrer: Marcel Schneider, Wolfgang Engels, Dr. Roland Boemer Vorsitzender des Aufsichtsrates: Martin Haering _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
