Getting a SAN need advice

[ICTNUT]

Hi All,

 

I am taking the plunge and am starting to gather info on SANS.

 

Here are my requirements:

 

SAN Size needs to be between 6Tb - 9Tb

I want to run Virtual Servers to replace aging physical servers.

 

What experiences do people have with SANs, what vendors would people suggest.

 

I have worked with large scale NAS for a while but SANs are a different beast so any info would be really apreciated

[torledo]

Hi All,

 

I am taking the plunge and am starting to gather info on SANS.

 

Here are my requirements:

 

SAN Size needs to be between 6Tb - 9Tb

I want to run Virtual Servers to replace aging physical servers.

 

What experiences do people have with SANs, what vendors would people suggest.

 

I have worked with large scale NAS for a while but SANs are a different beast so any info would be really apreciated

 

which large scale NAS have you used, if you have the budget for an entry-level enteprise NAS you could present virtual machines to you're servers over CIFS or NFS...it would require a very good performing NAS box however.

 

IF you choose to go down the iscsi route have a look at storevault or equalogic (dell). Most arrays now come with 750 or 1TB disks so you can get to 9TB quite easily with a dozen or disks in a single shelf. Infact a 6TB+ storevault S500/S550 ashok was mentioning in a previous thread sounds ideal - will do NAS and iSCSI. You can even specify a fiber channel starter kit if you want that option....it's not field upgradable so specify it on initial order.

 

No idea how much that would cost but would come in under 10k i would have thought.

[limbo]

I have just recieved a quote for a SAN - all HP kit, using our existing servers with fibre channel connections.

 

What I have found out that calling someting a SAN is like calling something a server - they can vary hugely because of the different variables you can have.

 

For me the important thing is the backup environment - we have lots of capacity still on the servers we have, but the backup takes way too long. so my focus is on having the parallel backup SAN to mirror the production SAN which I can then pull off to tape as and when without worrying about the performance of the network while this is happening.

 

European Electronique are guiding me through the process very nicely and taken the headache out of it by doing most of the hard work, recommending the hardware and configuration. They have done the installations in some of the new academies so they are old hands at it.

[torledo]

I have just recieved a quote for a SAN - all HP kit, using our existing servers with fibre channel connections.

 

What I have found out that calling someting a SAN is like calling something a server - they can vary hugely because of the different variables you can have.

 

For me the important thing is the backup environment - we have lots of capacity still on the servers we have, but the backup takes way too long. so my focus is on having the parallel backup SAN to mirror the production SAN which I can then pull off to tape as and when without worrying about the performance of the network while this is happening.

 

European Electronique are guiding me through the process very nicely and taken the headache out of it by doing most of the hard work, recommending the hardware and configuration. They have done the installations in some of the new academies so they are old hands at it.

 

to expand on that SAN replication can vary from vendor to vendor product to product. The cost of array based replication software should be factored in if you choose to go down that route. Using host based replication has performance implications in addition both host-based replication and d2d using a backup server requires thought and ofcourse advice from those with experience.

 

One of the things i like about something like the storevault is that it gives you various levels of backup and replication....on the one hand it does snapshots allowing you to rollback to previous point in time within the array, RAID-DP is RAID 6 without the performance penalty although consumes a lot of RAM and CPU i believe.

 

And to top it all array-based replication at no additional license cost other than the cost of additional filers...it also supports ndmp so backup to tape, gigabit tape library or to backup media server can be done using the very efficient ndmp protocol.

 

Whereas something like an entry level HP fc array limbo is talking about doesn't do multiprotocol and has the higher initial cost of fibre channel (x2 for the backup san) and fc hba's. Whereas D2D using dedicated backup VLAN with a multiprotocol device is cheaper and just as effective. Storevault replication would however be limited as to the options of sync/async and other advanced replication options that more expensive devices would have at significant cost.

[dhicks]

I want to run Virtual Servers to replace aging physical servers.

 

Coraid might be of interest:

 

Coraid :: The Linux Storage People

 

They provide SAN systems that use the ATA Over Ethernet protocol instead of iSCISI - less protocol overhead, cheaper hardware.

 

Personally, I'm of the opinion that SANs get over-used somewhat in virtual machine setups. A SAN is only going to be a benefit if the amount of processor power you need outweighs the amount of disk storage/performance you need (i.e. your processes are processor-bound, not disk-bound). A SAN lets multiple CPU units utilise a disk array, but at the expense of having to move more data back and forward over yet more hardware that you have to buy. I reckon most schools are more disk-bound than anything - multiple client machines loading Windows settings, documents, even photos or video, no actual processing needed, just disk performance. Might as well cut out the overhead and attach the disks straight to the processor, spend extra money on simply mirroring the setup for instant failover.

 

--

David Hicks

[torledo]

I think we've had this conversation before , but even schools with a modest number of servers soon find that with growth disk and array mgmt becomes unwieldy...as limbo said backup windows start to shrink when using a centralized backup device, virtualization and clusters are just one of the things you can do with a SAN not THE reason to have a san....

 

performance scalability is obviously going to be an issue...you'd want to have the ability to expand the number of interfaces for an iscsi array and for it to have significant cache RAM for those disk intensive operations from multiple servers....but with features like redundant controllers and the array based software i was mentioning they are seriously impressive bits of kit. Yes, they seem a lot of money for a device which is essentially presenting a disk volume to one or more servers, but storage islands are so lame and so last century that they're not worth putting up with these days.

[SeanVin]

We’ve just bought a pair of HP FC2012fc SANs, we got a very good deal that included the care packs to install them.

 

The main reasons I wanted a SAN was storage consolidation, scalability and redundancy. I am very interested in virtualisation, but I have wanted a SAN long before I discovered that they were a pre-requisite.

 

We considered iSCSI, but it runs over Ethernet, fibre channel is designed for fast throughput and has much higher bandwidth utilisation, in short 4gb fibre channel is more than 4 times faster than 1gb iSCSI. To my mind if I’m taking the hard drives off a very fast internal SCSI connection, I really want the fabric to be a fast as possible. Every time I Googled ‘Advantages of iSCSI’ there was only one answer ‘its cheaper’. Well I was told to make the network faster (10x!!!), future proof, and not to be constrained by budget, there was only one choice.

 

From my research it became very clear that setting up a SAN is not straight forward, even our consultants bottled-it and suggested getting specialists in. It was the care packs that sealed the HP deal.

Edited May 23, 2008 by SeanVin