On Sat, Apr 3, 2010 at 7:50 PM, Tim Cook <t...@cook.ms> wrote: > > > On Sat, Apr 3, 2010 at 6:53 PM, Robert Milkowski <mi...@task.gda.pl>wrote: > >> On 03/04/2010 19:24, Tim Cook wrote: >> >> >> >> On Fri, Apr 2, 2010 at 4:05 PM, Edward Ned Harvey < >> guacam...@nedharvey.com> wrote: >> >>> Momentarily, I will begin scouring the omniscient interweb for >>> information, but I’d like to know a little bit of what people would say >>> here. The question is to slice, or not to slice, disks before using them in >>> a zpool. >>> >>> >>> >>> One reason to slice comes from recent personal experience. One disk of a >>> mirror dies. Replaced under contract with an identical disk. Same model >>> number, same firmware. Yet when it’s plugged into the system, for an >>> unknown reason, it appears 0.001 Gb smaller than the old disk, and therefore >>> unable to attach and un-degrade the mirror. It seems logical this problem >>> could have been avoided if the device added to the pool originally had been >>> a slice somewhat smaller than the whole physical device. Say, a slice of >>> 28G out of the 29G physical disk. Because later when I get the >>> infinitesimally smaller disk, I can always slice 28G out of it to use as the >>> mirror device. >>> >>> >>> >>> There is some question about performance. Is there any additional >>> overhead caused by using a slice instead of the whole physical device? >>> >>> >>> >>> There is another question about performance. One of my colleagues said >>> he saw some literature on the internet somewhere, saying ZFS behaves >>> differently for slices than it does on physical devices, because it doesn’t >>> assume it has exclusive access to that physical device, and therefore caches >>> or buffers differently … or something like that. >>> >>> >>> >>> Any other pros/cons people can think of? >>> >>> >>> >>> And finally, if anyone has experience doing this, and process >>> recommendations? That is … My next task is to go read documentation again, >>> to refresh my memory from years ago, about the difference between “format,” >>> “partition,” “label,” “fdisk,” because those terms don’t have the same >>> meaning that they do in other OSes… And I don’t know clearly right now, >>> which one(s) I want to do, in order to create the large slice of my disks. >>> >> >> Your experience is exactly why I suggested ZFS start doing some "right >> sizing" if you will. Chop off a bit from the end of any disk so that we're >> guaranteed to be able to replace drives from different manufacturers. The >> excuse being "no reason to, Sun drives are always of identical size". If >> your drives did indeed come from Sun, their response is clearly not true. >> Regardless, I guess I still think it should be done. Figure out what the >> greatest variation we've seen from drives that are supposedly of the exact >> same size, and chop it off the end of every disk. I'm betting it's no more >> than 1GB, and probably less than that. When we're talking about a 2TB >> drive, I'm willing to give up a gig to be guaranteed I won't have any issues >> when it comes time to swap it out. >> >> >> that's what open solaris is doing more or less for some time now. >> >> look in the archives of this mailing list for more information. >> -- >> Robert Milkowski >> http://milek.blogspot.com >> >> > > Since when? It isn't doing it on any of my drives, build 134, and judging > by the OP's issues, it isn't doing it for him either... I try to follow this > list fairly closely and I've never seen anyone at Sun/Oracle say they were > going to start doing it after I was shot down the first time. > > --Tim >
Oh... and after 15 minutes of searching for everything from 'right-sizing' to 'block reservation' to 'replacement disk smaller size fewer blocks' etc. etc. I don't see a single thread on it. --Tim
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