Re: [zfs-discuss] ditto blocks for use data integrated in b61

2007-03-21 Thread Richard Elling

Robert Milkowski wrote:

Hello Richard,

Wednesday, March 21, 2007, 1:48:23 AM, you wrote:

RE Yes, PSARC 2007/121 integrated into build 61 (and there was much rejoicing 
:-)
RE I'm working on some models which will show the affect on various RAID
RE configurations and intend to post some results soon.  Suffice to say, if
RE you have a stripe with  1 disk, you might be able to survive loss of a
RE disk.  There are some other details which will need to be fleshed out, too.
RE More importantly, positioning this relative to the other options can be
RE confusing, and we're working on clear explainations to help avoid over-
RE exuberance.

Also I guess it would be possible to change copies once file system is
created, right? If it's so then people could get confused about which
data are protected and to what extent and which are not.


My understanding is that writes use the current copies parameter.  So, yes,
some people could be confused.  A good idea would be to set that policy at
file system creation time.


Perhaps 'zfs rewrite' would possibly help (someone working on this?).


Wouldn't that fall under the generic rewrite/shrink functionality we're also
anxiously waiting for?  Note that this also brings up a nasty edge case where
the rewrite may cause you to run out of space.
 -- richard

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Re: [zfs-discuss] ditto blocks for use data integrated in b61

2007-03-20 Thread Richard Elling

Yes, PSARC 2007/121 integrated into build 61 (and there was much rejoicing :-)
I'm working on some models which will show the affect on various RAID
configurations and intend to post some results soon.  Suffice to say, if
you have a stripe with  1 disk, you might be able to survive loss of a
disk.  There are some other details which will need to be fleshed out, too.
More importantly, positioning this relative to the other options can be
confusing, and we're working on clear explainations to help avoid over-
exuberance.
 -- richard

Robert Milkowski wrote:

Hello zfs-discuss,

  http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6459491

  I guess some people here will be happy :)


  ps. now think about all these questions: what do you think about HW
  RAID5 LUNs with raidz2 on top of this with ditto block set to 3? Or
  maybe 2 would be good enough? :))

  


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