Discussion:
snapmirroring over WAN
(too old to reply)
Lori Barfield
2005-11-10 16:49:38 UTC
Permalink
for offsite backups, we hope to snapmirror our new fas 3020 on
regular schedule via vpn over the internet to an older filer at our colo
obviously, intermittent latency is a concern since we don't have
dedicated link. and so is the potential for overpowering the modes
firewall/network hardware currently in place. does anyone have
suggestion for how we might throttle the snapmirrors to improv
reliability in the transmission

and how are you folks handling encryption for remote mirroring
we have a small pix, sonicwall, or cisco to choose from...i'
guessing we may have to try all three but i hope to pick the on
most likely to succeed the first time

..lor
Brian Parent
2005-11-10 17:08:06 UTC
Permalink
If I recall correctly, snapmirror uses very little bandwidth
and shouldn't be a problem on any modern network. It only copie
the blocks which were changed, rather than entire files

Re
> Date: Thu, 10 Nov 2005 08:49:38 -080
> From: Lori Barfield <***@gmail.com
> To: ***@mathworks.co
> Subject: snapmirroring over WA
>
> for offsite backups, we hope to snapmirror our new fas 3020 on
> regular schedule via vpn over the internet to an older filer at our colo
> obviously, intermittent latency is a concern since we don't have
> dedicated link. and so is the potential for overpowering the modes
> firewall/network hardware currently in place. does anyone have
> suggestion for how we might throttle the snapmirrors to improv
> reliability in the transmission
>
> and how are you folks handling encryption for remote mirroring
> we have a small pix, sonicwall, or cisco to choose from...i'
> guessing we may have to try all three but i hope to pick the on
> most likely to succeed the first time
>
>
> ...lor
Darren Dunham
2005-11-10 16:40:23 UTC
Permalink
>
> If I recall correctly, snapmirror uses very little bandwidth
> and shouldn't be a problem on any modern network.

Well, that depends on how much data is changing. It can certainl
overwhelm a slow WAN link if it's busy enough

However, you can throttle the rate at which it will attempt to send

You can specify a kbs figure for maximum bandwidth directly in th
snapmirror.conf file.
--
Darren Dunham ***@taos.co
Senior Technical Consultant TAOS http://www.taos.com
Got some Dr Pepper? San Francisco, CA bay are
< This line left intentionally blank to confuse you.
Frank, Jason
2005-11-10 17:36:52 UTC
Permalink
Well, that all depends on how many changed blocks you expect in a day
as well as what kind of link you have, how busy the link is currently
what exact model of PIX or Sonicwall you have, and what the operatin
hours of the business are

Snapmirror does include a throttle, but if you throttle it too much
you'll be perpetually behind. And if you don't throttle it enough, it'
about the same as not having one. It might be possible to do you
snapmirror overnight, if it's acceptable to your client, and no
throttle it at all. There are really a lot of options here

-----Original Message----
From: owner-***@mathworks.com [mailto:owner-***@mathworks.com
On Behalf Of Lori Barfiel
Sent: Thursday, November 10, 2005 10:50 A
To: ***@mathworks.co
Subject: snapmirroring over WA

for offsite backups, we hope to snapmirror our new fas 3020 on a regula
schedule via vpn over the internet to an older filer at our colo
obviously, intermittent latency is a concern since we don't have
dedicated link. and so is the potential for overpowering the modes
firewall/network hardware currently in place. does anyone have
suggestion for how we might throttle the snapmirrors to improv
reliability in the transmission

and how are you folks handling encryption for remote mirroring
we have a small pix, sonicwall, or cisco to choose from...i'm guessin
we may have to try all three but i hope to pick the one most likely t
succeed the first time

..lor
Lori Barfield
2005-11-10 17:47:22 UTC
Permalink
On 11/10/05, Frank, Jason <***@srcp.com> wrote
> Well, that all depends on how many changed blocks you expect in a day
> as well as what kind of link you have, how busy the link is currently
> what exact model of PIX or Sonicwall you have, and what the operatin
> hours of the business are

we're tri-continental. :

> Snapmirror does include a throttle, but if you throttle it too much
> you'll be perpetually behind. And if you don't throttle it enough, it'
> about the same as not having one. It might be possible to do you
> snapmirror overnight, if it's acceptable to your client, and no
> throttle it at all. There are really a lot of options here

yes, indeed. we don't have an "overnight," but from the on
data point i just received in response, it looks like we *might
not have trouble. we need to learn more about what we hav
here

i am concerned about snaps overlapping, of course, an
received the pointer from adam fox that some folks use a
admin host to monitor and control the firing of snap mirror
in order to prevent the problem

..lor
Darren Dunham
2005-11-10 17:05:29 UTC
Permalink
> Snapmirror does include a throttle, but if you throttle it too much
> you'll be perpetually behind. And if you don't throttle it enough, it'
> about the same as not having one. It might be possible to do you
> snapmirror overnight, if it's acceptable to your client, and no
> throttle it at all. There are really a lot of options here

Good point... I hadn't thought about doing things based on time lik
that

I've used the throttle by setting it just a little bit below the tota
size of the link. That way if we did a big load on the netapp, it woul
eventually sync up, but wouldn't saturate the link in the meantime
That left the link with a little bit of overhead for interactiv
traffic so it felt a lot better

--
Darren Dunham ***@taos.co
Senior Technical Consultant TAOS http://www.taos.com
Got some Dr Pepper? San Francisco, CA bay are
< This line left intentionally blank to confuse you.
Leeds, Daniel
2005-11-10 17:21:30 UTC
Permalink
yeah but that initial transfer can be fun if you are mirroring a couple terabyte volumes or if the application is generating alot of changes. a DS3 wan link would be no problem but they may need to rate limit snapmirror on much smaller wan links


-----Original Message----
From: owner-***@mathworks.com on behalf of Brian Paren
Sent: Thu 11/10/2005 9:08 A
To: ***@mathworks.co
Subject: Re: snapmirroring over WA

If I recall correctly, snapmirror uses very little bandwidth
and shouldn't be a problem on any modern network. It only copie
the blocks which were changed, rather than entire files

Re
> Date: Thu, 10 Nov 2005 08:49:38 -080
> From: Lori Barfield <***@gmail.com
> To: ***@mathworks.co
> Subject: snapmirroring over WA
>
> for offsite backups, we hope to snapmirror our new fas 3020 on
> regular schedule via vpn over the internet to an older filer at our colo
> obviously, intermittent latency is a concern since we don't have
> dedicated link. and so is the potential for overpowering the modes
> firewall/network hardware currently in place. does anyone have
> suggestion for how we might throttle the snapmirrors to improv
> reliability in the transmission
>
> and how are you folks handling encryption for remote mirroring
> we have a small pix, sonicwall, or cisco to choose from...i'
> guessing we may have to try all three but i hope to pick the on
> most likely to succeed the first time
>
>
> ...lor
Lori Barfield
2005-11-10 17:30:00 UTC
Permalink
On 11/10/05, Brian Parent <***@calvin.ucsd.edu> wrote
> If I recall correctly, snapmirror uses very little bandwidth
> and shouldn't be a problem on any modern network. It only copie
> the blocks which were changed, rather than entire files

ah yes, sorry that i didn't mention this point...we're doing a
initial ndmpcopy over a little gig switch here at the offic
before moving the filer to the colo

some of our data is going to be large image files, so w
aren't sure yet how much bandwidth the syncs are going t
want. i was more concerned about the jerks and jolts an
irregular paths you get when you fling data out into th
wild...not sure how well netapps handle hiccups in th
middle of snapping

..lor
Johnson, John T.
2005-11-10 17:46:07 UTC
Permalink
SnapMirror will consume as much bandwidth as it can get. I have a DS
between Minneapolis and Denver and SnapMirror will flood it 100% n
matter if it's a full or incremental transfer. The only difference i
how long it floods the pipe

There's two areas where you can change this. If you can set QOS on you
VPN link between Filers IP addresses and set a reasonable bandwidt
parameter, I would do that. Otherwise you can set in in Filerview whe
setting up the Snapmirror volume relationship under Maximum Transfe
Rate. This can be tedious as you have to set it on each replicate
volume. We set it on our Cisco router to run at 10 Mbit during the da
and automatically jump to 40 Mbit after 10:00 PM

I replicate Exchange and SQL data daily with logs getting replicate
every 2 hours. My delta changes are roughly 300 gigs per night and a
40 Mbits (the other 5 Mbits we reserve for AD replication and norma
network traffic), it takes about 6 hours. SnapMirror also doesn'
thread its transfers. It just blasts the pipe so if you can stagge
your transfers you should get better throughput

Good luck
Joh

-----Original Message----
From: owner-***@mathworks.com [mailto:owner-***@mathworks.com
On Behalf Of Lori Barfiel
Sent: Thursday, November 10, 2005 10:50 A
To: ***@mathworks.co
Subject: snapmirroring over WA

for offsite backups, we hope to snapmirror our new fas 3020 on a regula
schedule via vpn over the internet to an older filer at our colo
obviously, intermittent latency is a concern since we don't have
dedicated link. and so is the potential for overpowering the modes
firewall/network hardware currently in place. does anyone have
suggestion for how we might throttle the snapmirrors to improv
reliability in the transmission

and how are you folks handling encryption for remote mirroring
we have a small pix, sonicwall, or cisco to choose from...i'm guessin
we may have to try all three but i hope to pick the one most likely t
succeed the first time

..lor
Paul Galjan
2005-11-10 17:47:26 UTC
Permalink
Lori

ndmpcopy is not going to work. You can establish the snapmirro
relationship while the files are co-located tho. Another option i
snapmirror to tape

You can alway throttle snapmirror. Check the documentation for it o
how to do it. Another thing you're going to want to look at is th
snapmirror window size. The default window size is rather larger tha
what's appropriate for a WAN

As far as encryption goes, I thought you said you would be using
VPN, which presumably would take care of that

Lastly, if the data's already on a filer, then you can estimate th
amount of bandwidth it will require by snapshotting on the sam
schedule you plan to do snapmirror updates. Then you can do the mat
with snap delta (assuming you're running 7.x). Remember to accoun
for some amount of network overhead to account for packet headers an
retransmits and such

--pau

On 11/10/05, Lori Barfield <***@gmail.com> wrote

> ah yes, sorry that i didn't mention this point...we're doing a
> initial ndmpcopy over a little gig switch here at the offic
> before moving the filer to the colo

> some of our data is going to be large image files, so w
> aren't sure yet how much bandwidth the syncs are going t
> want. i was more concerned about the jerks and jolts an
> irregular paths you get when you fling data out into th
> wild...not sure how well netapps handle hiccups in th
> middle of snapping


> ...lor
Lai, Derek
2005-11-10 18:20:30 UTC
Permalink
Lori

Local initial snapmirror is a good idea whenever it's an option

I've setup DR to St. Louis first and now Plano, Texas and it's been ver
reliable. Snapmirroring is also pretty good at setting up a checkpoin
re-start if it has problem getting through. I am also pretty confiden
that it knows how to handle overlapping snapmirror. I've seen it happe
to us when there is networking problem. If it detects that
snapmirroring is still in progress it will not kick off the sam
snapmirror

Snapmirror has been really reliable. I've had lots more problem with th
WAN. The only problem I've seen with Snapmirror is when you run out o
disk space (We are using mostly qtree snapmirror)

Derek

-----Original Message----
From: owner-***@mathworks.com [mailto:owner-***@mathworks.com
On Behalf Of Lori Barfiel
Sent: Thursday, November 10, 2005 9:30 A
To: ***@mathworks.co
Subject: Re: snapmirroring over WA

On 11/10/05, Brian Parent <***@calvin.ucsd.edu> wrote
> If I recall correctly, snapmirror uses very little bandwidth, and
> shouldn't be a problem on any modern network. It only copies the
> blocks which were changed, rather than entire files

ah yes, sorry that i didn't mention this point...we're doing an initia
ndmpcopy over a little gig switch here at the office before moving th
filer to the colo

some of our data is going to be large image files, so we aren't sure ye
how much bandwidth the syncs are going to want. i was more concerne
about the jerks and jolts and irregular paths you get when you flin
data out into the wild...not sure how well netapps handle hiccups in th
middle of snapping

..lor
John Stoffel
2005-11-10 19:13:34 UTC
Permalink
Brian> If I recall correctly, snapmirror uses very little bandwidth
Brian> and shouldn't be a problem on any modern network. It onl
Brian> copies the blocks which were changed, rather than entire files

The problem is the initial copy, which takes forever if you have
small link and lots of files. We're running into this issue wit
Snapvault

Also, if you have a LFN (Large Fat Network) where you have both hig
bandwidth and high latency, then you run into TCP window scalin
issues.

Snapvault uses a 2mb TCP window by default I think, which is also th
max it can be. In my case, I want 4mb or higher.

Joh
John Stoffel - Senior Staff Systems Administrator - System LSI Grou
Toshiba America Electronic Components, Inc. - http://www.toshiba.com/tae
***@taec.toshiba.com - 508-486-108
John Stoffel
2005-11-10 19:16:41 UTC
Permalink
Henry> We also had to back up our volumes to a remote site vi
Henry> snapmirror accross a T1 WAN. One of the vols was over 1TB an
Henry> it would have taken days to create the initial baseline ove
Henry> the T1 so we snapped to SDLT tape, sent it down to CA an
Henry> created the baseline in a "snap"! Now our nightly VSMs tak
Henry> about 2 hours for 5 gigs (our average delta size)

Can you do this with SnapVaults, or just snapmirrors? This would be
great way to get an initial snapvault setup for my remote sites, sinc
they are on fast links, but far away and the TCP bandwidth delay i
killing my performance

Joh
Kevin Mascarenhas
2005-11-10 21:28:29 UTC
Permalink
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