From: Jonathan Tripathy <jonnyt@abpni.co.uk>
To: linux-lvm@redhat.com
Subject: Re: [linux-lvm] Snapshots and disk re-use
Date: Wed, 06 Apr 2011 01:50:35 +0100 [thread overview]
Message-ID: <4D9BB8DB.6070906@abpni.co.uk> (raw)
In-Reply-To: <4D9BB703.3030101@ankh.org>
On 06/04/2011 01:42, James Hawtin wrote:
> On 06/04/2011 00:28, Jonathan Tripathy wrote:
>> Ok, i think I get it now. At the minute, my vg (vg0) only has on PV
>> in it (/dev/md3 which you can tell is a mdadm RAID device). I wasn't
>> aware you could add more PVs (that's pretty cool!). So, let's say I
>> had a spare partition (/dev/hdb7 as an example). To my vg0 volume
>> group, I would firstly:
>>
>> pvcreate /dev/hdb7
>> vgextend /dev/hdb7
>
> Right however danger warnings are going off in my mind now!
>
>> Then, every time I create a new customer LV, I would do:
>>
>> lvcreate -nNewCustomerLV -L20G vg0 /dev/md3
>
> yes that would work
>
>>
>> Then, every time I wanted to create a snapshot:
>>
>> lvcreate -L20G -s -n data_snap /dev/vg0/NewCustomerLV /dev/hdb7
>>
>
> Yes
>
>> Is that correct? No Leakage? And no zeroing needed?
> Indeed
>
>>
>> Side note: Since I didn't partition my servers with this in mind, my
>> new PV will probably have to be an iSCSI device located on a remote
>> target :( Either that or use a loopback device with an image, but I'd
>> be scared that the system would not boot properly. Can you give me
>> any tips on how to use an image file as a PV just for snapshots?
>
> Ok, there has been alot of dangerous talk here, i assume you are using
> an md device so you can mirror things.
Correct
> If you added a single disk to that, and that disk failed you would
> have a major problem. Likewise if you rebooted with open snaps and
> iscsi you would need that iscsi device available during computer boot.
> I REALLY hope you do not have your local FS on the same vg as your
> data. As this would result in a non booting machine.
Nope. My root partition is not on LVM at all, but just on a regular md
partition. The LVM LVs are used for virtual machine hosting for
customers. Also, I used just /dev/hdb7 as an example, but it does bring
up some interesting questions:
If the PV used for snapshots were to fail while the snapshot was open,
or the server rebooted and the PV wasn't available at boot, what would
happen? I ask these questions because a loopback device or iSCSI is
really my only feasible option right now for the snapshot PV...
next prev parent reply other threads:[~2011-04-06 0:50 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-23 12:36 [linux-lvm] Snapshots and disk re-use Jonathan Tripathy
2011-02-23 13:09 ` Joe Thornber
2011-02-23 13:57 ` Jonathan Tripathy
2011-02-23 14:16 ` Joe Thornber
2011-02-23 14:18 ` Jonathan Tripathy
2011-02-23 16:12 ` Ray Morris
2011-02-23 16:55 ` Jonathan Tripathy
2011-02-23 17:54 ` Stuart D. Gathman
2011-02-23 18:05 ` Jonathan Tripathy
2011-02-23 19:34 ` Stuart D. Gathman
2011-02-23 18:05 ` Stuart D. Gathman
2011-02-23 18:19 ` Jonathan Tripathy
2011-02-23 18:39 ` Les Mikesell
2011-02-23 19:39 ` Stuart D. Gathman
2011-02-23 20:03 ` Les Mikesell
2011-02-23 20:37 ` Stuart D. Gathman
2011-02-23 20:49 ` Jonathan Tripathy
2011-02-23 23:25 ` Stuart D. Gathman
2011-02-23 23:42 ` Stuart D. Gathman
2011-02-24 0:09 ` Jonathan Tripathy
2011-02-24 0:32 ` Stuart D. Gathman
2011-02-24 0:37 ` Jonathan Tripathy
2011-02-24 0:40 ` Jonathan Tripathy
2011-02-24 2:00 ` Stuart D. Gathman
2011-02-24 7:33 ` Jonathan Tripathy
2011-02-24 14:50 ` Stuart D. Gathman
2011-02-24 14:57 ` Jonathan Tripathy
2011-02-24 15:13 ` Stuart D. Gathman
2011-02-24 15:20 ` Jonathan Tripathy
2011-02-24 16:41 ` Jonathan Tripathy
2011-02-24 19:15 ` Nataraj
2011-02-24 19:25 ` Les Mikesell
2011-02-24 19:55 ` Stuart D. Gathman
2011-02-24 19:19 ` Stuart D. Gathman
2011-02-24 19:45 ` Stuart D. Gathman
2011-02-24 21:22 ` Jonathan Tripathy
2011-04-05 20:09 ` Jonathan Tripathy
2011-04-05 20:41 ` Stuart D. Gathman
2011-04-05 20:48 ` Jonathan Tripathy
2011-04-05 20:59 ` James Hawtin
2011-04-05 21:36 ` Jonathan Tripathy
2011-04-05 22:42 ` James Hawtin
2011-04-05 22:52 ` Jonathan Tripathy
2011-04-05 23:11 ` James Hawtin
2011-04-05 23:19 ` Jonathan Tripathy
2011-04-05 23:39 ` James Hawtin
2011-04-06 0:00 ` Jonathan Tripathy
2011-04-06 0:08 ` Stuart D. Gathman
2011-04-06 0:14 ` Jonathan Tripathy
2011-04-06 0:16 ` James Hawtin
2011-04-06 0:28 ` Jonathan Tripathy
2011-04-06 0:38 ` Stuart D. Gathman
2011-04-06 0:43 ` Stuart D. Gathman
2011-04-06 1:36 ` James Hawtin
2011-04-06 1:47 ` Jonathan Tripathy
2011-04-06 1:53 ` James Hawtin
2011-04-06 0:47 ` Jonathan Tripathy
2011-04-06 0:42 ` James Hawtin
2011-04-06 0:50 ` Jonathan Tripathy [this message]
2011-04-06 1:20 ` James Hawtin
2011-04-06 1:45 ` Jonathan Tripathy
2011-02-23 19:49 ` Nataraj
2011-02-23 19:24 ` Stuart D. Gathman
2011-02-23 19:07 ` [linux-lvm] Problem executing lvm related commands Tinni
2011-02-23 19:33 ` [linux-lvm] Snapshots and disk re-use Phillip Susi
2011-02-23 19:45 ` Stuart D. Gathman
2011-02-23 19:56 ` Nataraj
2011-02-23 13:18 ` Sunil_Gupta2
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