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Is hot-syncing feasible?

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Mike Fisher_5
Trusted Contributor

Is hot-syncing feasible?

Hi all

One of our client's has posed this question to us:
[He's alrady got an hp-ux box + FC60]

"Do you have any knowledge of hot-syncing between FC60's?
We're looking as siting another system remotely
We want to replicate disc I/O to provide a 'warm' standby facility
This would have to be at disc controller level & NOT at database management level"

QUESTION: Is this feasible?

Regards - Mike
Don't get mad - get naked
10 REPLIES
Pete Randall
Outstanding Contributor
Solution

Re: Is hot-syncing feasible?

Mike,

(Almost didn't recognise you with the new hat!)

I don't think there is any sort of communication ability in the FC60 that would be able to tell the other FC60 what it's doing. Within a given FC60, you can set up RAID0/1 mirroring but between two FC60s, I don't think it can be done.

Sorry,


Pete


Pete
Tim Adamson_1
Honored Contributor

Re: Is hot-syncing feasible?

Mike,

This sounds like the SDRF (not 100% sure if I have the right term) functionality that EMC offer for their arrays.

I am not aware of the same offering for FC60.

The closest that HP would come is an offering with the XP array.


Cheers!
Yesterday is history, tomorrow is a mystery, today is a gift. That's why it's called the present.
Massimo Bianchi
Honored Contributor

Re: Is hot-syncing feasible?

Tim: yes, for EMC is called Source Remote Data Finder,SRDF, offered with 38xx family.
For IBM is RPPC, offered with the shark series.
For HP is Continuus Access, CA, offered with the XP series.

Mike:
The functionality that you are mentioning are only offered with high end storage, like the ones i have mentioned.

fc60 is rather old and do not have that add-on.
Long distance replication, over fibre, is very complex and expensive, for it is only found in high end (and not cheap) hardware.

Massimo
Bill Hassell
Honored Contributor

Re: Is hot-syncing feasible?

While this sounds simple enough, it is a very complicated (and usually extremely expensive). The complicated part is the software and/or firmware needed to handle everything. On the surface, the controller or computer writes data to the local disk and somehow creates a separate network packet for the remote system. Then everyone waits until an affirmative response comes back. If you use a modem, then expect performance to be 1000:1 slower (a 1 second update to the database may now take 15 minutes).

But what if the link goes down or becomes erratic? Without some sohpisticated code, your primary system will be hung or at least the integrity of the remote data may be in question.

And finally, can you afford a fast enough link to the remote location? The FC60's are much too fast for a T1 or DS3 line so you'll likely need a fiber link, perhaps costing $25-50,000 a month. Again, the massive impact of a slow link on your local system will determine how much you'd be willing to spend.

Now if the remote system is just in another building, it becomes a more reasonable design but now the question of how safe the remote location might be if a huge fire takes out everything. Distance becomes an important criteria in this case.

Bottom line is that the FC60's are not designed for any data replication capability. You'll need a much more sophisticated box such as the XP arrays and lots of extra cash to spend to reduce the impact on the local system. A good rule of thumb is: how much does each hour of downtime cost the company? Is it possible to survive a one day outage? If so, tapes in briefcase are pretty darn fast compared to the cost of transmitting 500Gb over a long distance.


Bill Hassell, sysadmin
Stefan Farrelly
Honored Contributor

Re: Is hot-syncing feasible?

Not with an FC60. You need to move up a couple of models sizewise to get this functionalily.

The XP is the top of the line and can do it with SRDF.

The next one down is the new EVA5000 which can do it with Continuous Access.

The FC60 is too dumb to do it.
Im from Palmerston North, New Zealand, but somehow ended up in London...
Mike Fisher_5
Trusted Contributor

Re: Is hot-syncing feasible?

By 'remote' I mean a different city
EVA5000 would therefore be the cheapest hp solution ?
Don't get mad - get naked
Stefan Farrelly
Honored Contributor

Re: Is hot-syncing feasible?

Yes, the EVA5000 is the minimum to get this functionality. Check it out at;

http://h18006.www1.hp.com/products/storageworks/enterprise/index.html
Im from Palmerston North, New Zealand, but somehow ended up in London...
Mike Fisher_5
Trusted Contributor

Re: Is hot-syncing feasible?

Thanks all - appreciated
Not many bunnies in this corner of the ITRC universe
Don't get mad - get naked
Vincent Fleming
Honored Contributor

Re: Is hot-syncing feasible?

Mike,

Actually, you will be able to use an EVA3000 very soon for such things...

But, for now at least (and last I heard), the EVA supports only Synchronous CA, which means that if you try to push the distance between systems over about 10-30 Km, you will begin to experience unacceptable response times. Synchronous mode requires that the disk subsystem (EVA) not acknowledge a write to the local host until it has successfully been transmitted (and acknowledged) by the remote disk array. If the remote site is far away, this can easily push your response times to 100ms or more. (NY to CA is about 100ms *each way*, giving you response times of >200ms!)

The EVA (both 3000 and 5000) are supposed to introduce Asynch CA within the next year. My guess is that it will be 1Q05 or later.

Meanwhile, you can use a CASA (Continuous Access SAN Appliance) to perform hardware mirroring with true Async - today. I think you can continue to use your FC60 as well.

Otherwise, there are other vendors that offer Async in the midrange today, such as EMC's Clariion line.

Good luck!

-Vince
No matter where you go, there you are.
Dave Wherry
Esteemed Contributor

Re: Is hot-syncing feasible?

Vincent beat me to it, once again. You can use CASA.
http://www.hp.com/products1/storage/products/virtualization_appliances/network/sv3000/index.html
CASA allows you to replicate between different arrays. Your FC60 could replicate to a VA7410 for example. Replication always had to be between like arrays, EMC to EMC, XP toXP and so on. CASA can do EMC to an XP.
Of course, it costs. Then again the FC60 is getting older and I'm sure maintenance costs on that are getting higher. You may want to look at a couple of new arrays in a replication setup. In the long run it might be cheaper.