First off, raidz2 and raidz1 with copies=2 are not the same thing. raidz2 will give you two copies of parity instead of just one. It also guarantees that this parity is on different drives. You can sustain 2 drive failures without data loss.
raidz1 with copies=2 will give you two copies of all your files, but there is no guarantee that they are on different drives, and you can still only sustain 1 drive failure. You'll have better space efficiency with raidz2 if you're using 9 drives. If I were you, I'd use your 9 disks as one big raidz, or better yet, get 10 disks, and make a stripe of 2 5 disk raidz's for the best performance. Save your SSD drive for the L2ARC (cache) or ZIL, you'll get better speed that way instead of throwing it away on a boot drive. -- -----Original Message----- From: owner-freebsd-sta...@freebsd.org [mailto:owner-freebsd-sta...@freebsd.org] On Behalf Of Damien Fleuriot Sent: January-05-11 5:01 AM To: Damien Fleuriot Cc: freebsd-stable@freebsd.org Subject: Re: ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks Hi again List, I'm not so sure about using raidz2 anymore, I'm concerned for the performance. Basically I have 9x 1.5T sata drives. raidz2 and 2x raidz1 will provide the same capacity. Are there any cons against using 2x raidz1 instead of 1x raidz2 ? I plan on using a SSD drive for the OS, 40-64gb, with 15 for the system itself and some spare. Is it worth using the free space for cache ? ZIL ? both ? @jean-yves : didn't you experience problems recently when using both ? --- Fleuriot Damien On 3 Jan 2011, at 16:08, Damien Fleuriot <m...@my.gd> wrote: > > > On 1/3/11 2:17 PM, Ivan Voras wrote: >> On 12/30/10 12:40, Damien Fleuriot wrote: >> >>> I am concerned that in the event a drive fails, I won't be able to >>> repair the disks in time before another actually fails. >> >> An old trick to avoid that is to buy drives from different series or >> manufacturers (the theory is that identical drives tend to fail at >> the same time), but this may not be applicable if you have 5 drives >> in a volume :) Still, you can try playing with RAIDZ levels and >> probabilities. >> > > That's sound advice, although one also hears that they should get > devices from the same vendor for maximum compatibility -.- > > > Ah well, next time ;) > > > A piece of advice I shall heed though is using 1% less capacity than > what the disks really provide, in case one day I have to swap a drive > and its replacement is a few kbytes smaller (thus preventing a rebuild). _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org" _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
