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Old 11-16-2011, 07:37 PM
"Smithies, Russell"
 
Default not using LVM for Linux VM guests?

I came across an old post comment yesterday (from http://echenh.blogspot.com/2010/04/how-to-extend-lvm-on-vmware-guest-os.html ) discussing the "hack" of LVM on Linux VM guests and whether it's better not to use it to simplify disk management.
I've re-posted the comment below, does it sound reasonable? Is it better to not use LVM on Linux VM guests?

--Russell


-----------------------------------------------------------
At my job, after doing the same kind of procedure graph, we began to ask ourselves, why are using a LVM on a Linux VM guests?

Since we're no longer living in the physical OS world, we didn't need to use the OS hacks(LVM) to overcome physical disk limitations anymore.
We decided to Just let the hypervisor and virtual storage do that work for us.

For example, in our production setup (3 tier commerce with VMs for database , webserver, and appserver), we're see a great improvement in managability and performance (>10%) by just dropping LVM, and most partitions.

In your example, the resize process is 7 functional steps:
1. Increase size of VMDK
2. In VM OS, Create Partition (??)
3. REBOOT (!!)
4. PVCreate
5. VGExtend
6. LVExtend
7. Resize2fs

Going to a LVM/partition-less setup reduces expansion to 3 steps and we don't need to take the VM OS offline!
1. Increase size of VMDK
2- Inside the VM, OS, rescan the scsi drive with:'echo 1 >/sys/class/scsi_device//rescan; dmesg' (dmesg will check that you drive isize has grown)
3- Resize2fs.

Our current disk arrangement has 3 VM HD devices
0 - small device (100M) with a single BOOT partition
1 - entire device is /
2 - entire device is SWAP

Doing this has simplified resizing so much, I now let the junior admins and my manager expand drive space as needed.

It's also let's us really be spartan on space since expansion is so quick. Instead of increasing systems in 30-50GB chunks, we can do 10-15GB and let our rmonitoring system warn us when space gets tight.
-------------------------------------------------------------

================================================== =====================
Attention: The information contained in this message and/or attachments
from AgResearch Limited is intended only for the persons or entities
to which it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipients is prohibited by AgResearch
Limited. If you have received this message in error, please notify the
sender immediately.
================================================== =====================
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Old 11-16-2011, 10:31 PM
"James A. Peltier"
 
Default not using LVM for Linux VM guests?

We use who disk LVM on our VMs. No partitioning except for the root disk which is separate for all our VMs. Since for us the root disks are largely static and all other components are on the full disk LVM volumes growing them doesn't require a reboot at all. Just rescan the scsi bus and resize. Done!

----- Original Message -----
| I came across an old post comment yesterday (from
| http://echenh.blogspot.com/2010/04/how-to-extend-lvm-on-vmware-guest-os.html
| ) discussing the "hack" of LVM on Linux VM guests and whether it's
| better not to use it to simplify disk management.
| I've re-posted the comment below, does it sound reasonable? Is it
| better to not use LVM on Linux VM guests?
|
| --Russell
|
|
| -----------------------------------------------------------
| At my job, after doing the same kind of procedure graph, we began to
| ask ourselves, why are using a LVM on a Linux VM guests?
|
| Since we're no longer living in the physical OS world, we didn't need
| to use the OS hacks(LVM) to overcome physical disk limitations
| anymore.
| We decided to Just let the hypervisor and virtual storage do that work
| for us.
|
| For example, in our production setup (3 tier commerce with VMs for
| database , webserver, and appserver), we're see a great improvement in
| managability and performance (>10%) by just dropping LVM, and most
| partitions.
|
| In your example, the resize process is 7 functional steps:
| 1. Increase size of VMDK
| 2. In VM OS, Create Partition (??)
| 3. REBOOT (!!)
| 4. PVCreate
| 5. VGExtend
| 6. LVExtend
| 7. Resize2fs
|
| Going to a LVM/partition-less setup reduces expansion to 3 steps and
| we don't need to take the VM OS offline!
| 1. Increase size of VMDK
| 2- Inside the VM, OS, rescan the scsi drive with:'echo 1
| >/sys/class/scsi_device//rescan; dmesg' (dmesg will check that you
| drive isize has grown)
| 3- Resize2fs.
|
| Our current disk arrangement has 3 VM HD devices
| 0 - small device (100M) with a single BOOT partition
| 1 - entire device is /
| 2 - entire device is SWAP
|
| Doing this has simplified resizing so much, I now let the junior
| admins and my manager expand drive space as needed.
|
| It's also let's us really be spartan on space since expansion is so
| quick. Instead of increasing systems in 30-50GB chunks, we can do
| 10-15GB and let our rmonitoring system warn us when space gets tight.
| -------------------------------------------------------------
|
| ================================================== =====================
| Attention: The information contained in this message and/or
| attachments
| from AgResearch Limited is intended only for the persons or entities
| to which it is addressed and may contain confidential and/or
| privileged
| material. Any review, retransmission, dissemination or other use of,
| or
| taking of any action in reliance upon, this information by persons or
| entities other than the intended recipients is prohibited by
| AgResearch
| Limited. If you have received this message in error, please notify the
| sender immediately.
| ================================================== =====================
| _______________________________________________
| CentOS mailing list
| CentOS@centos.org
| http://lists.centos.org/mailman/listinfo/centos

--
James A. Peltier
IT Services - Research Computing Group
Simon Fraser University - Burnaby Campus
Phone : 778-782-6573
Fax : 778-782-3045
E-Mail : jpeltier@sfu.ca
Website : http://www.sfu.ca/itservices
http://blogs.sfu.ca/people/jpeltier
I will do the best I can with the talent I have

_______________________________________________
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http://lists.centos.org/mailman/listinfo/centos
 
Old 11-17-2011, 10:35 AM
Dennis Jacobfeuerborn
 
Default not using LVM for Linux VM guests?

On 11/16/2011 09:37 PM, Smithies, Russell wrote:
> I came across an old post comment yesterday (from http://echenh.blogspot.com/2010/04/how-to-extend-lvm-on-vmware-guest-os.html ) discussing the "hack" of LVM on Linux VM guests and whether it's better not to use it to simplify disk management.
> I've re-posted the comment below, does it sound reasonable? Is it better to not use LVM on Linux VM guests?
>
> --Russell
>
>
> -----------------------------------------------------------
> At my job, after doing the same kind of procedure graph, we began to ask ourselves, why are using a LVM on a Linux VM guests?
>
> Since we're no longer living in the physical OS world, we didn't need to use the OS hacks(LVM) to overcome physical disk limitations anymore.
> We decided to Just let the hypervisor and virtual storage do that work for us.
>
> For example, in our production setup (3 tier commerce with VMs for database , webserver, and appserver), we're see a great improvement in managability and performance (>10%) by just dropping LVM, and most partitions.
>
> In your example, the resize process is 7 functional steps:
> 1. Increase size of VMDK
> 2. In VM OS, Create Partition (??)
> 3. REBOOT (!!)
> 4. PVCreate
> 5. VGExtend
> 6. LVExtend
> 7. Resize2fs
>
> Going to a LVM/partition-less setup reduces expansion to 3 steps and we don't need to take the VM OS offline!
> 1. Increase size of VMDK
> 2- Inside the VM, OS, rescan the scsi drive with:'echo 1>/sys/class/scsi_device//rescan; dmesg' (dmesg will check that you drive isize has grown)
> 3- Resize2fs.
>
> Our current disk arrangement has 3 VM HD devices
> 0 - small device (100M) with a single BOOT partition
> 1 - entire device is /
> 2 - entire device is SWAP
>
> Doing this has simplified resizing so much, I now let the junior admins and my manager expand drive space as needed.
>
> It's also let's us really be spartan on space since expansion is so quick. Instead of increasing systems in 30-50GB chunks, we can do 10-15GB and let our rmonitoring system warn us when space gets tight.

I'm not sure what the exact setup is but on the standard CentOS 5 setup you
can extend the space of a LVM-based guest without rebooting the guest.
Just add another virtual disk and it will immediately appear in the guest.
Set it up there as physical volume, add it to the main volume group and
then resize2fs the root filesystem. No restart or downtime required.

Regards,
Dennis

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Old 11-17-2011, 12:43 PM
Barry Brimer
 
Default not using LVM for Linux VM guests?

On Thu, 17 Nov 2011, Smithies, Russell wrote:

> I came across an old post comment yesterday (from http://echenh.blogspot.com/2010/04/how-to-extend-lvm-on-vmware-guest-os.html ) discussing the "hack" of LVM on Linux VM guests and whether it's better not to use it to simplify disk management.
> I've re-posted the comment below, does it sound reasonable? Is it better to not use LVM on Linux VM guests?
>
> --Russell
>
>
> -----------------------------------------------------------
> At my job, after doing the same kind of procedure graph, we began to ask ourselves, why are using a LVM on a Linux VM guests?
>
> Since we're no longer living in the physical OS world, we didn't need to use the OS hacks(LVM) to overcome physical disk limitations anymore.
> We decided to Just let the hypervisor and virtual storage do that work for us.
>
> For example, in our production setup (3 tier commerce with VMs for database , webserver, and appserver), we're see a great improvement in managability and performance (>10%) by just dropping LVM, and most partitions.
>
> In your example, the resize process is 7 functional steps:
> 1. Increase size of VMDK
> 2. In VM OS, Create Partition (??)
> 3. REBOOT (!!)
> 4. PVCreate
> 5. VGExtend
> 6. LVExtend
> 7. Resize2fs
>
> Going to a LVM/partition-less setup reduces expansion to 3 steps and we don't need to take the VM OS offline!
> 1. Increase size of VMDK
> 2- Inside the VM, OS, rescan the scsi drive with:'echo 1 >/sys/class/scsi_device//rescan; dmesg' (dmesg will check that you drive isize has grown)
> 3- Resize2fs.
>
> Our current disk arrangement has 3 VM HD devices
> 0 - small device (100M) with a single BOOT partition
> 1 - entire device is /
> 2 - entire device is SWAP
>
> Doing this has simplified resizing so much, I now let the junior admins and my manager expand drive space as needed.
>
> It's also let's us really be spartan on space since expansion is so quick. Instead of increasing systems in 30-50GB chunks, we can do 10-15GB and let our rmonitoring system warn us when space gets tight.
> -------------------------------------------------------------

One reason I choose to have separate filesystems which do use LVM instead
of VMware disks is that I can use different mount options. For example my
/tmp filesystems usually get noexec,nodev,nosuid .. with one
root filesystem that contains everything, you can't use mount options as
effectively. I also bind mount /var/tmp to /tmp for the same reason.

Barry
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Old 11-17-2011, 03:13 PM
Jon Detert
 
Default not using LVM for Linux VM guests?

Hello,

----- Original Message -----
> From: "Russell Smithies" <Russell.Smithies@agresearch.co.nz>
> To: "CentOS mailing list" <centos@centos.org>
> Sent: Wednesday, November 16, 2011 2:37:54 PM
> Subject: [CentOS] not using LVM for Linux VM guests?
>
> I came across an old post comment yesterday (from
> http://echenh.blogspot.com/2010/04/how-to-extend-lvm-on-vmware-guest-os.html
> ) discussing the "hack" of LVM on Linux VM guests and whether it's
> better not to use it to simplify disk management.
> I've re-posted the comment below, does it sound reasonable? Is it
> better to not use LVM on Linux VM guests?
>
> --Russell

I've had the same question. I've decided to continue to use LVM, for these 2 reasons:

1) my hypervisor, good, bad or indifferent, is VMware ESX 4.x and ESXi 4.x. Those hypervisors can't create virtual disks greater than 256 GB. So, if I want a file-system larger than 256 GB, I have to have some other software - LVM, in this case.

2) I like being able to give disk devices descriptive names, like /dev/mapper/zimbra-data instead of simply '/dev/sdb' or similar. There are probably ways other than LVM to do that, but LVM does offer that flexibility.

One thing I do avoid, however, is partitioning the virtual disks that might need to grow. This is because of the pain described in part below. The kernel often seems to have a hard time letting go of it's view of the partition table - either i have to umount the partition, or reboot. However, if i use the disk unpartitioned, the kernel has no prob, and I can *extend and/or resize*fs without umount or reboot.

- Jon

> -----------------------------------------------------------
> At my job, after doing the same kind of procedure graph, we began to
> ask ourselves, why are using a LVM on a Linux VM guests?
>
> Since we're no longer living in the physical OS world, we didn't need
> to use the OS hacks(LVM) to overcome physical disk limitations
> anymore.
> We decided to Just let the hypervisor and virtual storage do that
> work for us.
>
> For example, in our production setup (3 tier commerce with VMs for
> database , webserver, and appserver), we're see a great improvement
> in managability and performance (>10%) by just dropping LVM, and
> most partitions.
>
> In your example, the resize process is 7 functional steps:
> 1. Increase size of VMDK
> 2. In VM OS, Create Partition (??)
> 3. REBOOT (!!)
> 4. PVCreate
> 5. VGExtend
> 6. LVExtend
> 7. Resize2fs
>
> Going to a LVM/partition-less setup reduces expansion to 3 steps and
> we don't need to take the VM OS offline!
> 1. Increase size of VMDK
> 2- Inside the VM, OS, rescan the scsi drive with:'echo 1
> >/sys/class/scsi_device//rescan; dmesg' (dmesg will check that you
> drive isize has grown)
> 3- Resize2fs.
>
> Our current disk arrangement has 3 VM HD devices
> 0 - small device (100M) with a single BOOT partition
> 1 - entire device is /
> 2 - entire device is SWAP
>
> Doing this has simplified resizing so much, I now let the junior
> admins and my manager expand drive space as needed.
>
> It's also let's us really be spartan on space since expansion is so
> quick. Instead of increasing systems in 30-50GB chunks, we can do
> 10-15GB and let our rmonitoring system warn us when space gets
> tight.
> -------------------------------------------------------------
>
> ================================================== =====================
> Attention: The information contained in this message and/or
> attachments
> from AgResearch Limited is intended only for the persons or entities
> to which it is addressed and may contain confidential and/or
> privileged
> material. Any review, retransmission, dissemination or other use of,
> or
> taking of any action in reliance upon, this information by persons or
> entities other than the intended recipients is prohibited by
> AgResearch
> Limited. If you have received this message in error, please notify
> the
> sender immediately.
> ================================================== =====================
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
>
_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 11-17-2011, 03:53 PM
John Hodrien
 
Default not using LVM for Linux VM guests?

On Thu, 17 Nov 2011, Jon Detert wrote:

> One thing I do avoid, however, is partitioning the virtual disks that might
> need to grow. This is because of the pain described in part below. The
> kernel often seems to have a hard time letting go of it's view of the
> partition table - either i have to umount the partition, or reboot.
> However, if i use the disk unpartitioned, the kernel has no prob, and I can
> *extend and/or resize*fs without umount or reboot.

I think that's the main message to take away from this. There's no obvious
benefit of having partitions over having whole disks.

jh
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Old 11-17-2011, 06:04 PM
Paul Griffith
 
Default not using LVM for Linux VM guests?

On 11/17/2011 11:13 AM, Jon Detert wrote:
> Hello,
>
> ----- Original Message -----
>> From: "Russell Smithies"<Russell.Smithies@agresearch.co.nz>
>> To: "CentOS mailing list"<centos@centos.org>
>> Sent: Wednesday, November 16, 2011 2:37:54 PM
>> Subject: [CentOS] not using LVM for Linux VM guests?
>>
>> I came across an old post comment yesterday (from
>> http://echenh.blogspot.com/2010/04/how-to-extend-lvm-on-vmware-guest-os.html
>> ) discussing the "hack" of LVM on Linux VM guests and whether it's
>> better not to use it to simplify disk management.
>> I've re-posted the comment below, does it sound reasonable? Is it
>> better to not use LVM on Linux VM guests?
>>
>> --Russell
>
> I've had the same question. I've decided to continue to use LVM, for these 2 reasons:
>
> 1) my hypervisor, good, bad or indifferent, is VMware ESX 4.x and ESXi 4.x. Those hypervisors can't create virtual disks greater than 256 GB. So, if I want a file-system larger than 256 GB, I have to have some other software - LVM, in this case.

Just to clarify one thing with large virtual disks. The size limitation
is determined by the block size.

To create a file bigger than 256GB, the VMFS filesystem needs to have a
block size larger than 1MB. These are the maximums:

VMFS-3 (ESX/ESXi 4.x)

Block Size Maximum File Size
1 MB - 256 GB (default)
2 MB - 512 GB
4 MB - 1 TB
8 MB - 2 TB

http://kb.vmware.com/kb/1003565

With VMFS-5 has a maximum virtual disk size of 2TB minus 512B, with a 1
MB block size.

Cheers,
Paul
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http://lists.centos.org/mailman/listinfo/centos
 
Old 11-17-2011, 06:25 PM
"Smithies, Russell"
 
Default not using LVM for Linux VM guests?

> -----Original Message-----
> From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On
> Behalf Of Jon Detert
> Sent: Friday, 18 November 2011 5:13 a.m.
> To: CentOS mailing list
> Subject: Re: [CentOS] not using LVM for Linux VM guests?
>
> Hello,
>
> ----- Original Message -----
> > From: "Russell Smithies" <Russell.Smithies@agresearch.co.nz>
> > To: "CentOS mailing list" <centos@centos.org>
> > Sent: Wednesday, November 16, 2011 2:37:54 PM
> > Subject: [CentOS] not using LVM for Linux VM guests?
> >
> > I came across an old post comment yesterday (from
> > http://echenh.blogspot.com/2010/04/how-to-extend-lvm-on-vmware-
> guest-o
> > s.html
> > ) discussing the "hack" of LVM on Linux VM guests and whether it's
> > better not to use it to simplify disk management.
> > I've re-posted the comment below, does it sound reasonable? Is it
> > better to not use LVM on Linux VM guests?
> >
> > --Russell
>
> I've had the same question. I've decided to continue to use LVM, for these 2
> reasons:
>
> 1) my hypervisor, good, bad or indifferent, is VMware ESX 4.x and ESXi 4.x.
> Those hypervisors can't create virtual disks greater than 256 GB. So, if I want
> a file-system larger than 256 GB, I have to have some other software - LVM,
> in this case.
>
> 2) I like being able to give disk devices descriptive names, like
> /dev/mapper/zimbra-data instead of simply '/dev/sdb' or similar. There are
> probably ways other than LVM to do that, but LVM does offer that flexibility.
>
> One thing I do avoid, however, is partitioning the virtual disks that might
> need to grow. This is because of the pain described in part below. The
> kernel often seems to have a hard time letting go of it's view of the partition
> table - either i have to umount the partition, or reboot. However, if i use the
> disk unpartitioned, the kernel has no prob, and I can *extend and/or
> resize*fs without umount or reboot.
>
> - Jon

I have the same problem - I can never get the partition table reread without a reboot.
It's a little annoying as I can resize the disk on a Win2k8 VM without a reboot but not Linux :-(

--Russell
================================================== =====================
Attention: The information contained in this message and/or attachments
from AgResearch Limited is intended only for the persons or entities
to which it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipients is prohibited by AgResearch
Limited. If you have received this message in error, please notify the
sender immediately.
================================================== =====================
_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 11-17-2011, 06:28 PM
"Smithies, Russell"
 
Default not using LVM for Linux VM guests?

> -----Original Message-----
> From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On
> Behalf Of Paul Griffith
> Sent: Friday, 18 November 2011 8:04 a.m.
> To: centos@centos.org
> Subject: Re: [CentOS] not using LVM for Linux VM guests?
>
> On 11/17/2011 11:13 AM, Jon Detert wrote:
> > Hello,
> >
> > ----- Original Message -----
> >> From: "Russell Smithies"<Russell.Smithies@agresearch.co.nz>
> >> To: "CentOS mailing list"<centos@centos.org>
> >> Sent: Wednesday, November 16, 2011 2:37:54 PM
> >> Subject: [CentOS] not using LVM for Linux VM guests?
> >>
> >> I came across an old post comment yesterday (from
> >> http://echenh.blogspot.com/2010/04/how-to-extend-lvm-on-vmware-
> guest-
> >> os.html
> >> ) discussing the "hack" of LVM on Linux VM guests and whether it's
> >> better not to use it to simplify disk management.
> >> I've re-posted the comment below, does it sound reasonable? Is it
> >> better to not use LVM on Linux VM guests?
> >>
> >> --Russell
> >
> > I've had the same question. I've decided to continue to use LVM, for these
> 2 reasons:
> >
> > 1) my hypervisor, good, bad or indifferent, is VMware ESX 4.x and ESXi 4.x.
> Those hypervisors can't create virtual disks greater than 256 GB. So, if I want
> a file-system larger than 256 GB, I have to have some other software - LVM,
> in this case.
>
> Just to clarify one thing with large virtual disks. The size limitation is
> determined by the block size.
>
> To create a file bigger than 256GB, the VMFS filesystem needs to have a
> block size larger than 1MB. These are the maximums:
>
> VMFS-3 (ESX/ESXi 4.x)
>
> Block Size Maximum File Size
> 1 MB - 256 GB (default)
> 2 MB - 512 GB
> 4 MB - 1 TB
> 8 MB - 2 TB
>
> http://kb.vmware.com/kb/1003565
>
> With VMFS-5 has a maximum virtual disk size of 2TB minus 512B, with a 1 MB
> block size.
>
> Cheers,
> Paul

I just did the vSphere 5 "What's New" course and it looked they'd pumped all the maximums up to usable levels now.
Be nice if they could decide on a licensing model that made more sense...

--Russell
================================================== =====================
Attention: The information contained in this message and/or attachments
from AgResearch Limited is intended only for the persons or entities
to which it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipients is prohibited by AgResearch
Limited. If you have received this message in error, please notify the
sender immediately.
================================================== =====================
_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 11-17-2011, 07:07 PM
Alexander Dalloz
 
Default not using LVM for Linux VM guests?

Am 17.11.2011 20:25, schrieb Smithies, Russell:

> I have the same problem - I can never get the partition table reread without a reboot.
> It's a little annoying as I can resize the disk on a Win2k8 VM without a reboot but not Linux :-(

Next time simply use the partprobe command.

> --Russell

Alexander
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