for offsite backups, we hope to snapmirror our new fas 3020 on a 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 a dedicated link. and so is the potential for overpowering the modest firewall/network hardware currently in place. does anyone have a suggestion for how we might throttle the snapmirrors to improve 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 guessing we may have to try all three but i hope to pick the one most likely to succeed the first time.
...lori
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.
Re:
Date: Thu, 10 Nov 2005 08:49:38 -0800 From: Lori Barfield itdirector@gmail.com To: toasters@mathworks.com Subject: snapmirroring over WAN
for offsite backups, we hope to snapmirror our new fas 3020 on a 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 a dedicated link. and so is the potential for overpowering the modest firewall/network hardware currently in place. does anyone have a suggestion for how we might throttle the snapmirrors to improve 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 guessing we may have to try all three but i hope to pick the one most likely to succeed the first time.
...lori
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 certainly 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 the snapmirror.conf file.
On 11/10/05, Brian Parent bparent@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 initial ndmpcopy over a little gig switch here at the office before moving the filer to the colo.
some of our data is going to be large image files, so we aren't sure yet how much bandwidth the syncs are going to want. i was more concerned about the jerks and jolts and irregular paths you get when you fling data out into the wild...not sure how well netapps handle hiccups in the middle of snapping.
...lori
Lori,
ndmpcopy is not going to work. You can establish the snapmirror relationship while the files are co-located tho. Another option is snapmirror to tape.
You can alway throttle snapmirror. Check the documentation for it on how to do it. Another thing you're going to want to look at is the snapmirror window size. The default window size is rather larger than what's appropriate for a WAN.
As far as encryption goes, I thought you said you would be using a VPN, which presumably would take care of that.
Lastly, if the data's already on a filer, then you can estimate the amount of bandwidth it will require by snapshotting on the same schedule you plan to do snapmirror updates. Then you can do the math with snap delta (assuming you're running 7.x). Remember to account for some amount of network overhead to account for packet headers and retransmits and such.
--paul
On 11/10/05, Lori Barfield itdirector@gmail.com wrote:
ah yes, sorry that i didn't mention this point...we're doing an initial ndmpcopy over a little gig switch here at the office before moving the filer to the colo.
some of our data is going to be large image files, so we aren't sure yet how much bandwidth the syncs are going to want. i was more concerned about the jerks and jolts and irregular paths you get when you fling data out into the wild...not sure how well netapps handle hiccups in the middle of snapping.
...lori
Brian> If I recall correctly, snapmirror uses very little bandwidth, Brian> and shouldn't be a problem on any modern network. It only Brian> copies the blocks which were changed, rather than entire files.
The problem is the initial copy, which takes forever if you have a small link and lots of files. We're running into this issue with Snapvault.
Also, if you have a LFN (Large Fat Network) where you have both high bandwidth and high latency, then you run into TCP window scaling issues.
Snapvault uses a 2mb TCP window by default I think, which is also the max it can be. In my case, I want 4mb or higher.
John John Stoffel - Senior Staff Systems Administrator - System LSI Group Toshiba America Electronic Components, Inc. - http://www.toshiba.com/taec john.stoffel@taec.toshiba.com - 508-486-1087
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Brian Parent -
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Lori Barfield -
Paul Galjan