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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