Debian - DomU on ZFS

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Debian - DomU on ZFS

Net Warrior-2
Hi there .

I just come up with the need to migrate my LVM to zfs , when using LVM I
was able to reference my LV partitions as /dev/VG/LV,  then within the
configuration file I could reference the device as phy:/dev/VG/LV, now
with zfs I've got my disk and the pools as in , mypool/storage1,2,3 and
so on.

Now my question is.

I did not find any /dev/ reference to point to in the configuracion file
as in solaris, like /dev/zvol,  so, should I create an image file and
then install?
Will that methood downgrade my I/O  performance or will that be handled
bu the access methood I use? iSCSI, SAN Storage, Disk Type,  HBA,
network speed and so on.
Anyone already installed the combination of -> DomU+ZFS+Debian?

Ideas, suggestions?

Thanks in advance
Best Regards , thanks for your time and support.




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Re: Debian - DomU on ZFS

Fajar A. Nugraha-4
On Wed, Sep 14, 2011 at 10:50 AM, Net Warrior <[hidden email]> wrote:
> Hi there .
>
> I just come up with the need to migrate my LVM to zfs ,

Is this zfs-fuse, zfsonlinux, or did you switch the dom0 to
opensolaris, or did you have separate storage server with zfs?

> when using LVM I was
> able to reference my LV partitions as /dev/VG/LV,  then within the
> configuration file I could reference the device as phy:/dev/VG/LV, now with
> zfs I've got my disk and the pools as in , mypool/storage1,2,3 and so on.
>
> Now my question is.
>
> I did not find any /dev/ reference to point to in the configuracion file as
> in solaris, like /dev/zvol,  so, should I create an image file and then
> install?

zfs-fuse does not support zvols, and it's not recommended to store VM
images as files (trust me, I tried).

With zfsonlinux you WILL have /dev/zvol/mypool/storage1. That is,
assuming you either use Ubuntu ppa or latest source from git to
install zfsonlinux.

> Will that methood downgrade my I/O  performance or will that be handled bu
> the access methood I use? iSCSI, SAN Storage, Disk Type,  HBA, network speed
> and so on.

Roughly speaking, on the same hardware, using file image on zfs or
zvol, will make i/o performance drop by 50-75% compared to plain LVM.
Again, this is ROUGHLY based on my past tests. YMMV.

> Anyone already installed the combination of -> DomU+ZFS+Debian?

I have a dev system with xen+zvol+RHEL, as well as another one with
xen+zfs-fuse+RHEL.

--
Fajar

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Re: Debian - DomU on ZFS

Net Warrior-2
Thanks for your answer,

I have two scenarios.
One local server for testing purposes using zfs.
A SAN.

I think I will move forward with something like this,  disk=[
'iscsi:2011-09.us.example:server,xvda,w', ]
Do you think is this much more reasonable?
I think that for the local server that will be much better than using
images, do you agree?

Thank you very much.
Regards

El 09/14/2011 01:03 AM, Fajar A. Nugraha escribió:

> On Wed, Sep 14, 2011 at 10:50 AM, Net Warrior<[hidden email]>  wrote:
>> Hi there .
>>
>> I just come up with the need to migrate my LVM to zfs ,
> Is this zfs-fuse, zfsonlinux, or did you switch the dom0 to
> opensolaris, or did you have separate storage server with zfs?
>
>> when using LVM I was
>> able to reference my LV partitions as /dev/VG/LV,  then within the
>> configuration file I could reference the device as phy:/dev/VG/LV, now with
>> zfs I've got my disk and the pools as in , mypool/storage1,2,3 and so on.
>>
>> Now my question is.
>>
>> I did not find any /dev/ reference to point to in the configuracion file as
>> in solaris, like /dev/zvol,  so, should I create an image file and then
>> install?
> zfs-fuse does not support zvols, and it's not recommended to store VM
> images as files (trust me, I tried).
>
> With zfsonlinux you WILL have /dev/zvol/mypool/storage1. That is,
> assuming you either use Ubuntu ppa or latest source from git to
> install zfsonlinux.
>
>> Will that methood downgrade my I/O  performance or will that be handled bu
>> the access methood I use? iSCSI, SAN Storage, Disk Type,  HBA, network speed
>> and so on.
> Roughly speaking, on the same hardware, using file image on zfs or
> zvol, will make i/o performance drop by 50-75% compared to plain LVM.
> Again, this is ROUGHLY based on my past tests. YMMV.
>
>> Anyone already installed the combination of ->  DomU+ZFS+Debian?
> I have a dev system with xen+zvol+RHEL, as well as another one with
> xen+zfs-fuse+RHEL.
>


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Re: Debian - DomU on ZFS

Fajar A. Nugraha-4
On Wed, Sep 14, 2011 at 11:12 AM, Net Warrior <[hidden email]> wrote:

> Thanks for your answer,
>
> I have two scenarios.
> One local server for testing purposes using zfs.
> A SAN.
>
> I think I will move forward with something like this,  disk=[
> 'iscsi:2011-09.us.example:server,xvda,w', ]
> Do you think is this much more reasonable?
> I think that for the local server that will be much better than using
> images, do you agree?

Some aspects of that:
(1) file vs block
(2) Linux LVM vs zvol
(3) Local vs SAN (iscsi or whatever)

For (1), the usual answer is "it depends". block is usually better for
high load, but for some types of load and images file-backed can
perform better due to thin-provisioning and cache

For (2), if your ONLY concern is performance, with the same resources
LVM will win by huge margin. No brainer really. Just like ext4 will
have higher performance compared to zfs or btrfs. But if you want to
use zfs/zvol, I assume you already know about its features and
performance.

For (3), with the same resource (e.g. same number of disks), local
usually have high performance compare to SAN. Then again the resources
is usually NOT the same (e.g. a SAN is usually designed to have better
tiering with cache and such to provide better performance).

--
Fajar

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