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mdadm --grow
pwarren 
18/7/08 4:05:42 PM
Overlord

I was looking at the mdadm man page today and found:

--grow
Grow (or shrink) an array, or otherwise reshape it in some way. Currently supported growth options including changing the active size of component devices and changing the number of active devices in RAID levels 1/4/5/6, as well as adding or removing a write-intent bitmap.

I've been wondering when this sort of functionality would be available in the linux software raid subsystem for some time. now it's finally here, and I missed the meeting when it arrived!!

awesome stuff.

adding a new partitioned, same size disc:

$ mdadm /dev/md0 -a /dev/(new disk)
$ mdadm --grow /dev/md0 -n (old n + 1)

after you've swapped in your new bigger discs, syncing the array each time (tedious, but awesome!):

$ mdadm --grow /dev/md0 --size=max

then resize filesystem/lvm to suit :)

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wilsontc 
19/7/08 3:26:37 PM
Guru

This has been around for years afaik.

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iamthemaxx 
19/7/08 5:31:50 PM
Mod
SuperHero

Immortal


I was thinking the same thing, it's not new.

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pwarren 
19/7/08 6:21:21 PM
Overlord

oh boo-urs :(

I just came across it this week. 2.6.16 it was first implemented, guess that's a while ago.

anyways, will be good if I ever upgrade my storage server :)

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“Money is a powerful aphrodisiac. But flowers work almost as well.”
-- Lazarus Long

wilsontc 
20/7/08 5:18:17 PM
Guru

Maxx...should we tell him about ZFS now, or wait for him to say "Omg omg I just discovered ZFS!" in 2010?

It might even be in the Linux kernel by then :)

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Quote by Kothos

More importantly, do any of you girls like arse hair??



pwarren 
20/7/08 5:27:34 PM
Overlord

:(

I know about ZFS and use it at work. Was told we went to ZFS (raidz2 configuration) because linux software raid can't do a lot of things. But from what I can figure, the only thing it doesn't fix is the raid5 write hole.

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“Money is a powerful aphrodisiac. But flowers work almost as well.”
-- Lazarus Long

wilsontc 
25/7/08 8:52:47 PM
Guru

Quote by pwarren
:(

I know about ZFS and use it at work. Was told we went to ZFS (raidz2 configuration) because linux software raid can't do a lot of things. But from what I can figure, the only thing it doesn't fix is the raid5 write hole.



...and compression, online expansion*, built in quotas, unlimited number of easy-to-share filesystems, automatic mounting (no more fiddling with /etc/fstab) etc etc :)

*Some configurations of mdadm seem to do this better than others.

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Quote by Kothos

More importantly, do any of you girls like arse hair??



pwarren 
26/7/08 12:43:02 AM
Overlord

yeah, that's what I was getting at, mdadm and linux software raid can do all that, but ZFS can't. ZFS does get around the limitations of raid5 tho.

I could be completely wrong about that tho, I'm only just starting out in the world of storage systems.

-----
“Money is a powerful aphrodisiac. But flowers work almost as well.”
-- Lazarus Long

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