Normal practice on using SAN, just 1 or multiples

[macpiano]

In a normal enviroment and who knows what normal is but in our enviroment we have one san in each 2 of our subnets.  The other 3 do not have any but I use the disk space on the server itself. Is it normal to have to have 2 sans in each subnet. Understand that each subnet is a different building all with different IP addresses. My thinking is that since the SAN has a lot of redundacy and emails me and Dell when anything happens that that is about as good as  I can make it. I know it would be nice to be able to Vmotion the storage but not practical money wise. I can some pretty close to 2 esxi servers in each subnet but I have a 2 hour mission critical support with Dell and in our environment 2 hours would be find.

Just looking for some thoughts on this.

thanks

Gary

[Heimatplan]

Hi Gary,

I am struggling a littlebit to get the information out of your post, but I try to help you out: We have mission critical stuff running and our maximum fixtime is three hours. Without anyone working for three days we would be down and out.

To provide the uptime we have mirrored storage in two locations in different buildings on site and disaster recovery site as well. SAN is dual fabric. ESX public LAN is available in both datacenters. We can move every vm between them. We can provide enough power to customers with one datacenter completely gone. We dont loose any data with both datacenters completely gone. Each datacenter has two independent USV-Units. Each Datacenter is powered by a electric generator offering 48h backup time without refuling.

In case we loose data on the mirrored storage we are not able to get business back to work that quick because our tape backup would be to slow the restore everything in time. Regardless of the fact we can restore at about 200 MB per second. Its just not fast enough. But we can back 1/3 back to work after three hours. And 2/3 after 8 hours.

As a staring point: Imagine a fire burns down a building OR a fire strikes everything down in a location which is electrial located. How long would it take to get back everything to normal?

Ingo

[macpiano]

Does you datacenters have the same subnets? Ours will not so any vms moved will no longer communicate because their IPs would be different and we have stuff hosted to the outside are directed through a firewall that we do not have control of. DHCP also comes to mind as our provider does not let that work through the routers etc.

All our critical stuff is backed up to disk so a restore wouldn't be too bad. We are a school district and most buildings are 5-25 miles apart. The datacenter space we wil be renting will have one of them 50 miles away.

Thanks for your info. Although you have a larger scale deployment and I did say what really is "normal?" your info was what I was looking for.

thanks

gary

[eeg3]

Are your 2 SANs mirrored? If not, you may not be accomplishing the same thing that Heimatplan is. It sounds like he is running active/active, but I could be mistaken. None of Dell's SAN solutions provide an active/active setup (Equallogic nor Compellent), as far as I know. It sounds like you have 2 SANs that are separate, which will provide you with 50% of your storage staying online if one were to go down, assuming you're just operating completely independently. They could be replicating to each other, which would provide quicker recovery, though.

SAN availability is typically viewed as the number one priority when designing your storage architecture; more important than throughput or IOPS. Of course, different businesses have different needs. This is really something your business owners would need to determine more than IT: how long can our business operate without our systems? Active/active is great, but typically expensive. Your SAN vendor is a great resource when planning/architecting things like this.

[Heimatplan]

eeg3: Yes, it's an active/active setup with an IBM SVC doing the mirroring.

macpiano: Yes, the datacenters share the same subnets. For the DMZ Stuff we got a dedicated Network offering basically the same layout. Two locations, same subnet on both sides and two ISP-Connection on each datacenter. Everything is running on fixed IP.