Re: Re[2]: [zfs-discuss] Re: ZFS and Storage
Robert, PT You really need some level of redundancy if you're using HW raid. PT Using plain stripes is downright dangerous. 0+1 vs 1+0 and all PT that. Seems to me that the simplest way to go is to use zfs to mirror PT HW raid5, preferably with the HW raid5 LUNs being completely PT independent disks attached to completely independent controllers PT with no components or datapaths in common. well, it will give you less than half your raw storage. Due to costs I belive in most cases it won't be acceptable. People are using raid-5 mostly due to costs and you are proposing something worse (in terms of available logical storage) than mirroring. I realise that, but the question was about what combination of ZFS redundancy and HW-raid redundancy made sense. My point was that putting no redundancy at all at the HW-raid layer was a really bad idea, and the self-healing capability of zfs means that you want a level of redundancy within zfs. So you are inevitably going to lose some extra capacity. Which is better - zfs raidz on hardware mirrors, or zfs mirror on hardware raid-5? I wouldn't rule out raidz (or even raidz2) across multiple arrays that are HW-raid5 internally. My real concern there is the small random read performance issue. -- -Peter Tribble L.I.S., University of Hertfordshire - http://www.herts.ac.uk/ http://www.petertribble.co.uk/ - http://ptribble.blogspot.com/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: Re[2]: [zfs-discuss] Re: ZFS and Storage
Which is better - zfs raidz on hardware mirrors, or zfs mirror on hardware raid-5? The latter. With a mirror of RAID-5 arrays, you get: (1) Self-healing data. (2) Tolerance of whole-array failure. (3) Tolerance of *at least* three disk failures. (4) More IOPs than raidz of hardware mirrors (see Roch's blog entry). (5) More convenient FRUs (the whole array becomes a FRU). Jeff ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: Re[2]: [zfs-discuss] Re: ZFS and Storage
On Wed, 2006-06-28 at 14:55 -0700, Jeff Bonwick wrote: Which is better - zfs raidz on hardware mirrors, or zfs mirror on hardware raid-5? The latter. With a mirror of RAID-5 arrays, you get: (1) Self-healing data. (2) Tolerance of whole-array failure. (3) Tolerance of *at least* three disk failures. (4) More IOPs than raidz of hardware mirrors (see Roch's blog entry). (5) More convenient FRUs (the whole array becomes a FRU). Jeff Not that I disagree with the inital assessment, but a couple of corrections: (1) Both give you this. (2) ZFS RAIDZ on HW mirrors can also survive a complete HW mirror array failure. (3) Both configs can survive AT LEAST 3 drive failures. RAIDZ of HW mirrors is slightly better at being able to survive 4+ drive failures, statistically speaking. -- Erik Trimble Java System Support Mailstop: usca14-102 Phone: x17195 Santa Clara, CA Timezone: US/Pacific (GMT-0800) ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
