Messages in this thread | | | Date | Sun, 17 Jun 2007 10:28:02 -0700 (PDT) | From | dean gaudet <> | Subject | Re: limits on raid |
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On Sun, 17 Jun 2007, Wakko Warner wrote:
> dean gaudet wrote: > > On Sat, 16 Jun 2007, Wakko Warner wrote: > > > > > When I've had an unclean shutdown on one of my systems (10x 50gb raid5) it's > > > always slowed the system down when booting up. Quite significantly I must > > > say. I wait until I can login and change the rebuild max speed to slow it > > > down while I'm using it. But that is another thing. > > > > i use an external write-intent bitmap on a raid1 to avoid this... you > > could use internal bitmap but that slows down i/o too much for my tastes. > > i also use an external xfs journal for the same reason. 2 disk raid1 for > > root/journal/bitmap, N disk raid5 for bulk storage. no spindles in > > common. > > I must remember this if I have to rebuild the array. Although I'm > considering moving to a hardware raid solution when I upgrade my storage.
you can do it without a rebuild -- that's in fact how i did it the first time.
to add an external bitmap:
mdadm --grow --bitmap /bitmapfile /dev/mdX
plus add "bitmap=/bitmapfile" to mdadm.conf... as in:
ARRAY /dev/md4 bitmap=/bitmap.md4 UUID=dbc3be0b:b5853930:a02e038c:13ba8cdc
you can also easily move an ext3 journal to an external journal with tune2fs (see man page).
if you use XFS it's a bit more of a challenge to convert from internal to external, but see this thread:
http://marc.theaimsgroup.com/?l=linux-xfs&m=106929781232520&w=2
i found that i had to do "sb 1", "sb 2", ..., "sb N" for all sb rather than just the "sb 0" that email instructed me to do.
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