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On Thu, May 28, 2015 at 1:03 PM, Peter Humphrey <peter@××××××××××××.uk> wrote: |
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> On Thursday 28 May 2015 15:36:04 I wrote: |
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>> On Thursday 28 May 2015 08:44:27 Rich Freeman wrote: |
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>> > With an approach like yours, mdadm will attempt to create md1 by |
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>> > looking ONLY at sda1 and sdb1, and if that pair forms a valid array it |
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>> > is started, and if not it is not. If you add a new drive to your |
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>> > system or for whatever reason the kernel/udev rules change a little or |
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>> > some race condition changes a little then your devices might get |
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>> > different names, and the array will not be assembled. |
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>> |
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>> Hmm. I wonder if that's what's happening to me. Perhaps I'd better adopt |
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>> UUIDs then, once I work out what mine are. Thanks for the advice. |
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> |
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> I've found blkid, which tells me the UUIDs of my various devices, thus: |
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> |
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> # blkid /dev/md7 |
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> /dev/md7: UUID="ycGMf9-hEP2-tjT4-AtkJ-n8RI-pZ44-RqvlEY" |
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> TYPE="LVM2_member" |
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Just keep in mind that the UUID that goes into mdadm.conf might not be |
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the same UUID returned by blkid. I'm honestly not certain either way. |
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You can get the mdadm ID from mdadm --detail --scan. |
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> |
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> Two odd things: |
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> 1. /dev/md7 is the physical volume in which logical volumes are defined, |
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> so I'm surprised to see TYPE="LVM2_member". |
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I'm pretty sure this is fine. It recognizes it as an LVM pv, so that |
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makes it an LVM2 member. |
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> 2. There is no entry corresponding to /dev/md7 under /dev/disk/by-uuid, |
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> though /dev/md1 and /dev/md5 do have entries there [1]. |
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udev may be configured to not create uuid symlinks for LVM pvs (since |
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you wouldn't directly mount them anyway). The others contain |
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filesystems and do get symlinks. |
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> |
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> What should I be doing about this? |
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I'd probably just edit your mdadm.conf to be more liberal with |
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scanning, and add the arrays output by mdadm --detail --scan to your |
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config file. That alone may make your problems go away, and it should |
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be pretty harmless. |
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> |
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> I assume that the ../../dm-N links refer to the LVs - there are 15 of them. |
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> md7 is conspicuous by its absence. This seems like a problem to me, and it |
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> may account for /dev/md7 sometimes not being started at boot time. |
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> |
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LVM is just a wrapper around DM, so that is normal. Nothing about |
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what you've written here concerns me. |
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-- |
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Rich |
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