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[linux-lvm] Re: Re: Loopback mount a disk image with lvm (Girish)



Thanks Dave,
This worked like a charm.
Girish


On Mon, Jun 9, 2008 at 6:10 AM,  <linux-lvm-request redhat com> wrote:
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> Today's Topics:
>
>   1. striping question (Mag Gam)
>   2. Loopback mount a disk image with lvm (Girish V)
>   3. Re: Loopback mount a disk image with lvm (David Robinson)
>   4. Re: Performance tunning on LVM2 (Heinz Mauelshagen)
>   5. Re: Performance tunning on LVM2 (Antony MARTINEAU)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 7 Jun 2008 11:39:09 -0400
> From: "Mag Gam" <magawake gmail com>
> Subject: [linux-lvm] striping question
> To: linux-lvm redhat com
> Message-ID:
>        <1cbd6f830806070839l436b0b4ai99d3c4264e896ea6 mail gmail com>
> Content-Type: text/plain; charset="utf-8"
>
> If I am using x RAID 5 volumes and create PVs. Once I create the LVs is it a
> good idea to stripe them? If so, what is a valid stripe size?
>
> I am looking for performance BTW.
>
>
> TIA
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> ------------------------------
>
> Message: 2
> Date: Sun, 8 Jun 2008 18:23:23 -0400
> From: "Girish V" <girish xen gmail com>
> Subject: [linux-lvm] Loopback mount a disk image with lvm
> To: linux-lvm redhat com
> Message-ID:
>        <2122f0920806081523w7a7ce274q9707992948f6e1b4 mail gmail com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Hello,
>
> I have a disk.img (a disk image file, raw format) with the following "fdisk -l"
>
>    Device Boot      Start         End      Blocks   Id  System
> disk.img1   *           1          13      104391   83  Linux
> disk.img2              14        2491    19904535   8e  Linux LVM
>
> Now I can loopback mount the first bartition using
> "mount -o loop,offset=32256 disk.img /mnt".
>
> I need to mount the second partition. If the secoond partition had
> been an ext3 partition, I would have loopback mounted it as
> "mount -o loop,offset=$((255*63*512*13) disk.img /mnt", but when I try
> that, I get
> mount: unknown filesystem type 'LVM2_member'
>
> Any help is greatly appreciated.
>
> Thanks.
>
>
>
> ------------------------------
>
> Message: 3
> Date: Mon, 9 Jun 2008 10:52:54 +1000
> From: "David Robinson" <zxvdr au gmail com>
> Subject: Re: [linux-lvm] Loopback mount a disk image with lvm
> To: "LVM general discussion and development" <linux-lvm redhat com>
> Message-ID:
>        <b072968d0806081752s79f32e66h4c6d7de1b42094a0 mail gmail com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> On Mon, Jun 9, 2008 at 8:23 AM, Girish V <girish xen gmail com> wrote:
>> Hello,
>>
>> I have a disk.img (a disk image file, raw format) with the following "fdisk -l"
>>
>>    Device Boot      Start         End      Blocks   Id  System
>> disk.img1   *           1          13      104391   83  Linux
>> disk.img2              14        2491    19904535   8e  Linux LVM
>>
>> Now I can loopback mount the first bartition using
>> "mount -o loop,offset=32256 disk.img /mnt".
>>
>> I need to mount the second partition. If the secoond partition had
>> been an ext3 partition, I would have loopback mounted it as
>> "mount -o loop,offset=$((255*63*512*13) disk.img /mnt", but when I try
>> that, I get
>> mount: unknown filesystem type 'LVM2_member'
>>
>> Any help is greatly appreciated.
>
> losetup /dev/loop0 disk.img
> kpartx -a /dev/loop0
>
> Then to mount the first partition:
>
> mount /dev/mapper/loop0p1 /mnt
>
> Or to activate the volume group then mount the logical volume:
>
> vgscan
> vgchange -ay vg
> mount /dev/vg/lv /mnt
>
> Hope that helps.
>
> --Dave
>
>
>
> ------------------------------
>
> Message: 4
> Date: Mon, 9 Jun 2008 11:44:53 +0200
> From: Heinz Mauelshagen <mauelshagen redhat com>
> Subject: Re: [linux-lvm] Performance tunning on LVM2
> To: LVM general discussion and development <linux-lvm redhat com>
> Message-ID: <20080609094453 GA5507 redhat com>
> Content-Type: text/plain; charset=us-ascii
>
> On Fri, Jun 06, 2008 at 08:03:51AM -0700, Larry Dickson wrote:
>> A (linear) volume group made of two physical volumes consists of one PV
>> followed by the other, rather like a "Raid-Linear". If you size the
>> origin logical volume right, you can get one LV (the origin) to fall on one
>> disk, and force the snapshot to land on the other disk. This eliminates
>> back-and-forth seeking to the COW. Whether it solves your problem will
>> depend on how smart the driver is about the read-before-write activity on
>> the origin volume.
>>
>> Other members of the list may have more experience on this. Comments?
>
> If I read correctly, Antony just has *ONE* PV.
>
> So no matter what, he has to add another to allow for snapshot COW
> store allocation on that other PV, distinct from the one holding
> the origin(s). Presumably there's no other bottleneck aside from the
> disk, that'll do better.
>
> Keep in mind, that unless you've got streaming writes, the performance
> won't drop as much as in the (artificial) dd test below.
>
> FYI: With the current snapshot implementation, multiple snapshots per single
>     origin will throttle write performance because of write duplication
>     to all per snapshot COW stores.
>
> Heinz
>
>>
>> Larry
>>
>> On 6/6/08, Antony MARTINEAU <Antony MARTINEAU lippi fr> wrote:
>> >
>> >
>> > The volume group vg0 is the raid0 of two disk (SAS 15000rpm 300G0)
>> > I have only this raid on the server
>> >
>> > But i don't understand, imagine i make a volume group  ou of this raid0. It
>> > is no possible to snapshot the original volume, am i wrong?
>> >
>> > If i make a new VG on another disks, For exemple /dev/vg1/
>> > LVM don't permit to store a snaphot on a different VG than the origin
>> > volum.
>> >
>> > for exemple /dev/vg0/test cant be snapshoting on /dev/vg1/test.snap
>> >
>> > LV test and LV test.snap must be on the same volume, am i wrong ???? so it
>> > is impossible to store snapshot on another disk....
>> >
>> >
>> >   Cordialement,
>> >
>> >    *MARTINEAU
>> > Antony*
>> > Service informatique
>> > Assistant informatique
>> > LIPPI Management La Fouillouse
>> > 16440 Mouthiers sur Boheme
>> > Tel.: 05.45.67.34.35
>> > Courriel: *antony martineau lippi fr* <antony martineau lippi fr>*
>> > **http://www.lippi.fr* <http://www.lippi.fr/>
>> >
>> >
>> >
>> >   De : "Larry Dickson" <ldickson cuttedge com> Pour : "LVM general
>> > discussion and development" <linux-lvm redhat com> Date: 06/06/2008 16:19 Objet
>> > : Re: [linux-lvm] Performance tunning on LVM2
>> > ------------------------------
>> >
>> >
>> >
>> > This looks like the result of excessive seeking. Are origin volume and
>> > snapshot both on the same physical drive? Is it possible to make a volume
>> > group out of two drives, and arrange things so that origin volume and
>> > snapshot are hitting different disks?
>> >
>> > Larry Dickson
>> > Cutting Edge Networked Storage
>> >
>> > On 6/6/08, *Antony MARTINEAU* <*Antony MARTINEAU lippi fr*<Antony MARTINEAU lippi fr>>
>> > wrote:
>> >
>> > Hello,
>> > My configuration:
>> > Server DELL 2860 Intel(R) Xeon(R) CPU  X3230 @ 2.66GHz (Quad Core)
>> > 8GB of  memory
>> > 2 x SAS 15000 300G0 RAID 0 hardware
>> > SLES 10 SP2
>> > Kernel 2.6.16.60-0.21-xen
>> >
>> > i have one volume group vg0 ( whith one PV, the two disks in raid0) whith
>> > many lvm
>> > I am very surprise about LVM2 performance when a snapshot is done.
>> > Write speed on the Original volume is very bad when a snaphot is active...
>> >
>> > For exemple:
>> > *
>> > Speed on /dev/vg0/test when there is NO snapshot :*
>> >
>> > suse2:~ # dd if=/dev/zero of=/dev/vg0/test bs=2M count=400
>> > 400+0 records in
>> > 400+0 records out
>> > 838860800 bytes (839 MB) copied, 6.42741 seconds, 131 MB/s
>> > *
>> > Speed on /dev/vg0/test when there is one snapshot of this original volume :
>> > *
>> >
>> > suse2:~ # lvremove --force /dev/vg0/test3.snap
>> >  Logical volume "test3.snap" successfully removed
>> > suse2:~ # dd if=/dev/zero of=/dev/vg0/test bs=2M count=400
>> > 400+0 records in
>> > 400+0 records out
>> > 838860800 bytes (839 MB) copied, 6.42741 seconds, 131 MB/s
>> > suse2:~ # lvcreate -s -L1G -ntest.snap /dev/vg0/test
>> >  Logical volume "test.snap" created
>> > suse2:~ # dd if=/dev/zero of=/dev/vg0/test bs=2M count=400
>> > 400+0 records in
>> > 400+0 records out
>> > 838860800 bytes (839 MB) copied, 204.862 seconds, 4.1 MB/s
>> >
>> > *
>> > Speed on /dev/vg0/test when there is 2 snapshots of this original volume :
>> > *
>> >
>> > suse2:~ # lvcreate -s -L1G -ntest1.snap /dev/vg0/test
>> >  Logical volume "test1.snap" created
>> > suse2:~ # lvcreate -s -L1G -ntest2.snap /dev/vg0/test
>> >  Logical volume "test2.snap" created
>> > suse2:~ # lvremove /dev/vg0/test2.snap
>> > Do you really want to remove active logical volume "test2.snap"? [y/n]: y
>> >  Logical volume "test2.snap" successfully removed
>> > suse2:~ # dd if=/dev/zero of=/dev/vg0/test bs=2M count=400
>> > 400+0 records in
>> > 400+0 records out
>> > 838860800 bytes (839 MB) copied, 270.928 seconds, 3.1 MB/s
>> >
>> >
>> > Do you know  some elements about tunning performance?,?
>> >
>> > Performances are disastrous when a snaphot is active
>> > Could you give your speed result? and your amelioration??
>> >
>> > ps:Results are the same whithout Kernel Xen and whith a kernel more recent
>> > (*2.6.24.2* <http://2.6.24.2/>)  Cordialement,
>> >    *MARTINEAU
>> > Antony*
>> > Service informatique
>> > Assistant informatique
>> > LIPPI Management La Fouillouse
>> > 16440 Mouthiers sur Boheme
>> > Tel.: 05.45.67.34.35
>> > Courriel: *antony martineau lippi fr* <antony martineau lippi fr>*
>> > **http://www.lippi.fr* <http://www.lippi.fr/>
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
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>> >
>> >
>> > _______________________________________________
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>> > **https://www.redhat.com/mailman/listinfo/linux-lvm*<https://www.redhat.com/mailman/listinfo/linux-lvm>
>> > read the LVM HOW-TO at *http://tldp.org/HOWTO/LVM-HOWTO/*<http://tldp.org/HOWTO/LVM-HOWTO/>
>> > _______________________________________________
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>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
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>> >
>
>
>
>
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> ------------------------------
>
> Message: 5
> Date: Mon, 9 Jun 2008 12:06:19 +0200
> From: Antony MARTINEAU <Antony MARTINEAU lippi fr>
> Subject: Re: [linux-lvm] Performance tunning on LVM2
> To: mauelshagen redhat com,     LVM general discussion and development
>        <linux-lvm redhat com>
> Message-ID:
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