On Sat, 28 Mar 2009, Tim wrote:
#1: yes, there is harm as he may very well run into inconsistent performance which is a complete PITA to track down when you've got differing raidtypes underlying a volume.
Inconsistent performance can come from many things, including a single balky disk drive. The small difference between RAID types does not seem like enough to worry about. If it was a mix between raidz2 and mirrors then there is more cause for concern.
It is true that if the performance of the vdevs is not well balanced, then some vdevs could fill up faster than others when the system is under extremely heavy write loads.
#2: raidz2 isn't always "wise" to choose. It's a matter of performance, space, security requirements. 7+1 is fine for raidz1. If he was pushing 10 data disks that'd be another story.
Many in the industry have already declared RAID5 to be "unsafe at any speed" with today's huge SATA disk drives. The data recovery model for raidz1 is similar to RAID5. If the user can afford it, then raidz2 offers considerably more peace of mind.
If you are using 750GB+ SATA drives then your "7+1 is fine for raidz1" notion does not seem so bright.
Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
