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
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