[linux-lvm] Flexible storga: LVM setup on top of mdadm sets. Good idea or not?
bluca at comedia.it
Tue Jul 24 08:48:20 UTC 2007
On Mon, Jul 23, 2007 at 12:43:17PM -0400, Stuart D. Gathman wrote:
>On Mon, 23 Jul 2007, Luca Berra wrote:
>> On Sun, Jul 22, 2007 at 02:57:33PM -0400, Stuart D. Gathman wrote:
>> >The main drawback to md raid1 is that it always resynchronizes
>> >the *entire* partition when a disk goes offline temporarily. I also
>> False. md uses bitmaps to avoid this.
>I am using md on dozens of systems up through Centos-5. If there are any
>bitmaps, they don't work. Or maybe they are a new feature not in kernel
>2.6.18. The only change I've noticed since RH7.3 is that sync speed is no
>longer limited to 10K. Or maybe I'm not looking at the right thing.
Bitmaps are a feature of md since mdadm-2.0 (kernel 2.6.13 or 2.6.14)
>How would I see these bitmaps in action?
mdadm -G /dev/md?? -b internal
>BTW, to upgrade a 7.2 system to Centos5, I plan to install on a disk
>with matching partition sizes and replace boot drive. Is there any
>chance that md raid1 will sync from the old system overtop the new?
>(Because the new wouild have lower sequence numbers?) Or is there some
>kind of UUID in the raid superblock to prevent this? (Of course I plan
>to change partition types away from RAID Auto just to be safe...)
unfortunately redhat insisted for a long time on using the in-kernel md
auto-detect, which iirc just ignores md uuid. i think this is still true
changing partition type will prevent this
creating the new raid with a different minor will prevent this
or change the minor of the old raid.
... but we're getting offtopic.
if you have further questions post them on linux-raid.
Luca Berra -- bluca at comedia.it
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