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Mounting read-only snapshots using open-iscsi?

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dlambert at bmtcarhaul

Nov 12, 2008, 5:41 AM

Post #1 of 8 (3075 views)
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Mounting read-only snapshots using open-iscsi?

We acquired a cluster of NetApp filers a few months ago with only an
iSCSI license (no NFS or CIFS access), intending to use it for data
volumes on our Linux and Windows hosts and later for virtualization. We
have one production Gentoo system mounting a data volume from the filer
using open-iscsi, and we have several other Gentoo and Ubuntu systems
that we would like to configure that way as well.

We also have an Ubuntu system connected to a tape library. We would
like to take snapshots of the data-volumes that need to be backed up,
mount those snapshots on the backup host, and do an incremental backup
from the mounted filesystem.

Probably we would partition each LUN with one Linux partition, and put
an ext3 or reiserfs filesystem with a cluster-unique label on that
partition. Then we could take a set of snapshots for the backup, map
all the snapshot LUNs to the backup-host, do iSCSI discovery on the
backup-host, mount each partition (listed in a configuration-file) with
a "mount LABEL=..." command, perform the backup, unmount the partition,
do an iSCSI logout, and delete all the snapshots.

Has anyone gotten a setup like this to work?

--

David Lee Lambert

Software Developer, Precision Motor Transport Group, LLC

517-349-3011 x223 (work) ... 586-873-8813 (cell)

romeotheriault at gmail

Nov 12, 2008, 7:10 AM

Post #2 of 8 (2967 views)
Permalink

Re: Mounting read-only snapshots using open-iscsi? [In reply to]

I'm not 100% sure of this, but I don't think you can map and mount a
snapshot itself. (I may be wrong, someone please let me know if I am) but I
believe that you'll need a flexclone license to create a clone of that
particular snapshot and then map the clone to your backup host.

On Wed, Nov 12, 2008 at 8:41 AM, David L. Lambert
<dlambert [at] bmtcarhaul>wrote:

> We acquired a cluster of NetApp filers a few months ago with only an
> iSCSI license (no NFS or CIFS access), intending to use it for data volumes
> on our Linux and Windows hosts and later for virtualization. We have one
> production Gentoo system mounting a data volume from the filer using
> open-iscsi, and we have several other Gentoo and Ubuntu systems that we
> would like to configure that way as well.
>
>
>
> We also have an Ubuntu system connected to a tape library. We would like
> to take snapshots of the data-volumes that need to be backed up, mount those
> snapshots on the backup host, and do an incremental backup from the mounted
> filesystem.
>
>
>
> Probably we would partition each LUN with one Linux partition, and put an
> ext3 or reiserfs filesystem with a cluster-unique label on that partition.
> Then we could take a set of snapshots for the backup, map all the snapshot
> LUNs to the backup-host, do iSCSI discovery on the backup-host, mount each
> partition (listed in a configuration-file) with a "mount LABEL=…" command,
> perform the backup, unmount the partition, do an iSCSI logout, and delete
> all the snapshots.
>
>
>
> Has anyone gotten a setup like this to work?
>
>
>
> *--***
>
> *David Lee Lambert*
>
> *Software Developer, Precision Motor Transport Group, LLC*
>
> *517-349-3011 x223 (work) … 586-873-8813 (cell)*
>
>
>

--
Romeo Theriault

ulk at forsmark

Nov 12, 2008, 7:31 AM

Post #3 of 8 (2968 views)
Permalink

SV: Mounting read-only snapshots using open-iscsi? [In reply to]

Hmm.

I think it will be easier to buy a NFS license and just mount the flexvol containing the LUNs on the backup-server, then dump /mountpoint/.hourly-1/ or whatever.
Running a Gentoo/Ubuntu/Linux shop without a NFS license seems odd, it's like buying a car without wheels...

/Ulf

-----Ursprungligt meddelande-----
Från: owner-toasters [at] mathworks [mailto:owner-toasters [at] mathworks] För Romeo Theriault
Skickat: den 12 november 2008 16:11
Till: David L. Lambert; Toasters
Ämne: Re: Mounting read-only snapshots using open-iscsi?

I'm not 100% sure of this, but I don't think you can map and mount a snapshot itself. (I may be wrong, someone please let me know if I am) but I believe that you'll need a flexclone license to create a clone of that particular snapshot and then map the clone to your backup host.

On Wed, Nov 12, 2008 at 8:41 AM, David L. Lambert <dlambert [at] bmtcarhaul> wrote:

We acquired a cluster of NetApp filers a few months ago with only an iSCSI license (no NFS or CIFS access), intending to use it for data volumes on our Linux and Windows hosts and later for virtualization. We have one production Gentoo system mounting a data volume from the filer using open-iscsi, and we have several other Gentoo and Ubuntu systems that we would like to configure that way as well.

We also have an Ubuntu system connected to a tape library. We would like to take snapshots of the data-volumes that need to be backed up, mount those snapshots on the backup host, and do an incremental backup from the mounted filesystem.

Probably we would partition each LUN with one Linux partition, and put an ext3 or reiserfs filesystem with a cluster-unique label on that partition. Then we could take a set of snapshots for the backup, map all the snapshot LUNs to the backup-host, do iSCSI discovery on the backup-host, mount each partition (listed in a configuration-file) with a "mount LABEL=..." command, perform the backup, unmount the partition, do an iSCSI logout, and delete all the snapshots.

Has anyone gotten a setup like this to work?

--

David Lee Lambert

Software Developer, Precision Motor Transport Group, LLC

517-349-3011 x223 (work) ... 586-873-8813 (cell)

--
Romeo Theriault

jack1729 at gmail

Nov 12, 2008, 8:07 AM

Post #4 of 8 (2966 views)
Permalink

Re: Mounting read-only snapshots using open-iscsi? [In reply to]

I think you can mount an iscsi lun snapshot, but I would assume you
would have to do a lun restore (license included) and manage it as a
new lun (zoning) etc.

I assume your backup solution can't support / doesn't have an ndmp license?

I assume you have been backing up data via the host now and you are
trying to eliminate the overhead of the backup job on that host?

On 11/12/08, David L. Lambert <dlambert [at] bmtcarhaul> wrote:
> We acquired a cluster of NetApp filers a few months ago with only an
> iSCSI license (no NFS or CIFS access), intending to use it for data
> volumes on our Linux and Windows hosts and later for virtualization. We
> have one production Gentoo system mounting a data volume from the filer
> using open-iscsi, and we have several other Gentoo and Ubuntu systems
> that we would like to configure that way as well.
>
>
>
> We also have an Ubuntu system connected to a tape library. We would
> like to take snapshots of the data-volumes that need to be backed up,
> mount those snapshots on the backup host, and do an incremental backup
> from the mounted filesystem.
>
>
>
> Probably we would partition each LUN with one Linux partition, and put
> an ext3 or reiserfs filesystem with a cluster-unique label on that
> partition. Then we could take a set of snapshots for the backup, map
> all the snapshot LUNs to the backup-host, do iSCSI discovery on the
> backup-host, mount each partition (listed in a configuration-file) with
> a "mount LABEL=..." command, perform the backup, unmount the partition,
> do an iSCSI logout, and delete all the snapshots.
>
>
>
> Has anyone gotten a setup like this to work?
>
>
>
> --
>
> David Lee Lambert
>
> Software Developer, Precision Motor Transport Group, LLC
>
> 517-349-3011 x223 (work) ... 586-873-8813 (cell)
>
>
>
>

--
Sent from Gmail for mobile | mobile.google.com

Adam.Fox at netapp

Nov 12, 2008, 8:13 AM

Post #5 of 8 (2968 views)
Permalink

RE: Mounting read-only snapshots using open-iscsi? [In reply to]

That is mostly correct. Even though you don't want to write to the LUN,
the underlying OS needs to think it can write to it in order to mount it
(even if you mount it ro). Flex Clone solves this issue. If you don't
have a flex clone license, you should be able to do a lun create -b with
the snapshot name and create a snapshot-backed LUN which you could then
map to the backup server and do your backup.

Either will work.

-- Adam Fox
adamfox [at] netapp

From: Romeo Theriault [mailto:romeotheriault [at] gmail]
Sent: Wednesday, November 12, 2008 10:11 AM
To: David L. Lambert; Toasters
Subject: Re: Mounting read-only snapshots using open-iscsi?

I'm not 100% sure of this, but I don't think you can map and mount a
snapshot itself. (I may be wrong, someone please let me know if I am)
but I believe that you'll need a flexclone license to create a clone of
that particular snapshot and then map the clone to your backup host.

On Wed, Nov 12, 2008 at 8:41 AM, David L. Lambert
<dlambert [at] bmtcarhaul> wrote:

We acquired a cluster of NetApp filers a few months ago with only an
iSCSI license (no NFS or CIFS access), intending to use it for data
volumes on our Linux and Windows hosts and later for virtualization. We
have one production Gentoo system mounting a data volume from the filer
using open-iscsi, and we have several other Gentoo and Ubuntu systems
that we would like to configure that way as well.

We also have an Ubuntu system connected to a tape library. We would
like to take snapshots of the data-volumes that need to be backed up,
mount those snapshots on the backup host, and do an incremental backup
from the mounted filesystem.

Probably we would partition each LUN with one Linux partition, and put
an ext3 or reiserfs filesystem with a cluster-unique label on that
partition. Then we could take a set of snapshots for the backup, map
all the snapshot LUNs to the backup-host, do iSCSI discovery on the
backup-host, mount each partition (listed in a configuration-file) with
a "mount LABEL=..." command, perform the backup, unmount the partition,
do an iSCSI logout, and delete all the snapshots.

Has anyone gotten a setup like this to work?

--

David Lee Lambert

Software Developer, Precision Motor Transport Group, LLC

517-349-3011 x223 (work) ... 586-873-8813 (cell)

--
Romeo Theriault

dlambert at bmtcarhaul

Nov 12, 2008, 8:22 AM

Post #6 of 8 (2983 views)
Permalink

RE: Mounting read-only snapshots using open-iscsi? [In reply to]

On an instance of the NetApp Simulator, I was able to take a snapshot,
export it via NFS, create a loopback device based on the snapshot, and
mount the filesystem within it; something like:

Filer> lun create -b /vol/vol1/luns/lun11 -o noreserve
/vol/vol1/luns/lun11_snapforback

Filer> lun share /vol/vol1/luns/lun11_snapforback read

Linux> mount 10.10.10.23:/vol/vol1 /mnt/netapp-vol1

Linux> losetup -f /mnt/nasim9-vol1/luns/lun11_snapforback

Linux> kpartx -a /dev/loop1

Linux> mount /dev/loop1p5 /mnt/lun11-snap

However, as I said, we don't have an NFS license; we've also heard that
NFS performance is poorer than iSCSI performance. My guess is that some
commands like the following ought to work:

Filer> lun map /vol/vol1/luns/lun11_snapforback linux-host 3

Linux> iscsiadm -m discovery --interface eth0 -t st -p 10.10.10.23
--login

Linux> iscsiadm -m node --interface eth0 -p 10.10.10.23 --login

Linux> mount /dev/sde /mnt/lun11-snap

When I do that, though, the set of available SCSI disk devices on the
Linux host doesn't change. Perhaps this is an open-iscsi limitation
instead?

To answer Jack's questions:

We had Bacula working on the backup-host, and it doesn't support NDMP. I
don't think that would be any use for a LUN (which is just an opaque
file to the NetApp), anyway.

Yes, we do want to avoid the overhead of the backup job on the host, and
traffic across two network links when only one should be necessary. We
also want to make as few software changes on the other hosts as
possible.

We don't have a FlexClone license.

--

David Lee Lambert

Software Developer, Precision Motor Transport Group, LLC

517-349-3011 x223 (work) ... 586-873-8813 (cell)

________________________________

From: Romeo Theriault [mailto:romeotheriault [at] gmail]
Sent: Wednesday, November 12, 2008 10:11 AM
To: David L. Lambert; Toasters
Subject: Re: Mounting read-only snapshots using open-iscsi?

I'm not 100% sure of this, but I don't think you can map and mount a
snapshot itself. (I may be wrong, someone please let me know if I am)
but I believe that you'll need a flexclone license to create a clone of
that particular snapshot and then map the clone to your backup host.

On Wed, Nov 12, 2008 at 8:41 AM, David L. Lambert
<dlambert [at] bmtcarhaul> wrote:

[...]

We also have an Ubuntu system connected to a tape library. We would
like to take snapshots of the data-volumes that need to be backed up,
mount those snapshots on the backup host, and do an incremental backup
from the mounted filesystem.

Probably we would partition each LUN with one Linux partition, and put
an ext3 or reiserfs filesystem with a cluster-unique label on that
partition. Then we could take a set of snapshots for the backup, map
all the snapshot LUNs to the backup-host, do iSCSI discovery on the
backup-host, mount each partition (listed in a configuration-file) with
a "mount LABEL=..." command, perform the backup, unmount the partition,
do an iSCSI logout, and delete all the snapshots.

--
Romeo Theriault

dlambert at bmtcarhaul

Nov 12, 2008, 1:29 PM

Post #7 of 8 (2977 views)
Permalink

RE: Mounting read-only snapshots using open-iscsi? [In reply to]

I got mounting a snapshot to work. I needed to do "iscsiadm ...
--rescan", following this hint:

http://www.mail-archive.com/open-iscsi [at] googlegroups/msg01072.html

We have not implemented this with an actual NetApp yet, so I have no
idea whether performance will be acceptable; but thanks to all for the
advice.

--

David Lee Lambert

Software Developer, Precision Motor Transport Group, LLC

517-349-3011 x223 (work) ... 586-873-8813 (cell)

________________________________

From: owner-toasters [at] mathworks [mailto:owner-toasters [at] mathworks]
On Behalf Of David L. Lambert
Sent: Wednesday, November 12, 2008 11:22 AM
To: toasters [at] mathworks
Subject: RE: Mounting read-only snapshots using open-iscsi?

[...]

However, as I said, we don't have an NFS license; we've also heard that
NFS performance is poorer than iSCSI performance. My guess is that some
commands like the following ought to work:

Filer> lun map /vol/vol1/luns/lun11_snapforback linux-host 3

Linux> iscsiadm -m discovery --interface eth0 -t st -p 10.10.10.23
--login

Linux> iscsiadm -m node --interface eth0 -p 10.10.10.23 --login

Linux> mount /dev/sde /mnt/lun11-snap

When I do that, though, the set of available SCSI disk devices on the
Linux host doesn't change. Perhaps this is an open-iscsi limitation
instead?

ggwalker at mindspring

Nov 12, 2008, 5:00 PM

Post #8 of 8 (2968 views)
Permalink

RE: Mounting read-only snapshots using open-iscsi? [In reply to]

I hate to say it, because iSCSI is cool as hell and 'just works', but
you're better off just using NFS if you can get a license... It ain't
cheap tho. And FWIW, iSCSI could be faster than NFS, NFS is likely just
as fast as iSCSI or faster in some cases.

Utilizing the lun create -b (as in your example below), re-mounting that
newly exposed iSCSI LUN as a new device on LINUX then performing the
backup is definitely the right idea. This is the 'norm' for most NetApp
iSCSI environments (Exchange, SQL, etc).

Glenn

________________________________

From: owner-toasters [at] mathworks [mailto:owner-toasters [at] mathworks]
On Behalf Of David L. Lambert
Sent: Wednesday, November 12, 2008 4:29 PM
To: toasters [at] mathworks
Subject: RE: Mounting read-only snapshots using open-iscsi?

I got mounting a snapshot to work. I needed to do "iscsiadm ...
--rescan", following this hint:

http://www.mail-archive.com/open-iscsi [at] googlegroups/msg01072.html

We have not implemented this with an actual NetApp yet, so I have no
idea whether performance will be acceptable; but thanks to all for the
advice.

--

David Lee Lambert

Software Developer, Precision Motor Transport Group, LLC

517-349-3011 x223 (work) ... 586-873-8813 (cell)

________________________________

From: owner-toasters [at] mathworks [mailto:owner-toasters [at] mathworks]
On Behalf Of David L. Lambert
Sent: Wednesday, November 12, 2008 11:22 AM
To: toasters [at] mathworks
Subject: RE: Mounting read-only snapshots using open-iscsi?

[...]

However, as I said, we don't have an NFS license; we've also heard that
NFS performance is poorer than iSCSI performance. My guess is that some
commands like the following ought to work:

Filer> lun map /vol/vol1/luns/lun11_snapforback linux-host 3

Linux> iscsiadm -m discovery --interface eth0 -t st -p 10.10.10.23
--login

Linux> iscsiadm -m node --interface eth0 -p 10.10.10.23 --login

Linux> mount /dev/sde /mnt/lun11-snap

When I do that, though, the set of available SCSI disk devices on the
Linux host doesn't change. Perhaps this is an open-iscsi limitation
instead?

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