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bexter
Contributor
Contributor

Deciding on a SAN

Hi All, I would like to find out what criterai to use when deciding on a SAN sorage for VI3? After deciding on the SAN storage to use, how do you then configure it for best performance (e,g, RAID levels, LUN sizes, number of VM's per LUN and e.t.c? I have also read about the Netapps Array, they have this flexiclone tool, that creates 100 vms in 2min without using extra storage space. Is this to good to be true, what are the overheads if any (i.e. do the vms have the same perfomance as other on different SANs)?

cheers

bex

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3 Replies
RParker
Immortal
Immortal

You are asking lots of excellent questions, however, the biggest stipulation is money. How much do you want to spend? There are SAN devices and then there are $AN devices Smiley Happy

Netapp is good, but $500,000 for a good average priced SAN. Dell sells EMC/Clarion which has been considered a good choice. Much cheaper I would call DELL, get their advice, and go from there (you don't have to buy a DELL/EMC, but they can certainly answer your questions about ballpark figures and give you a good starting point).

RAID configuration RAID 5 is best practice, but lookup wikipedia and see the difference between RAID 4 and RAID 5 (same principle, but the parity is written to 1 drive vs entire array). RAID 5 is good in general, but can impact performance during writes. Netapp prefers RAID 4, because of this. They also offer double parity (2 drives that keep the parity in case your parity drive fails).

The more spindles the better. Netapp supports 28 disks in a RAID group (part of Aggregate), and you can actually setup multiple RAID groups, across Multiple Aggregates, across multiple drives, across multiple data stores on ESX, so this gets VERY complicated, VERY quickly.

LUNS you setup based upon size of the drive, there are many places on here you can get best practice size for LUNS, so I won't try to cover that, but suffice to say a LUN should give ample storage for your VM's.

You need to plan, that is the key.

2 questions.

How big are your VM's going to be,

Are your VM's memory intensive, Disk intensive or both?

That will help you determine the best course for your VM's. People say you need to keep LUNS small, I disagree. I have 1.1 ~ 1.3 TB LUNS. The thing about VMs you don't have to wait for the entire LUN to be restored to use the VM's, you can restore 1, and get that going while the others restore.. there are many other reasons I like larger LUNS myself, but everyone has their own opinion.

Netapp has a "thin" provisioning so you can have basically unlimited storage and the volumes expand based upon need, which is what I believe that flexiclone is. I don't think this is a good idea in the long run, you need some sort of limit, and yes you will run out of storage, but it's easier to simply configure your LUN to a set size and leave it. Rather than having the SAN run amuk... that gets crazy.

Netapp is the worlds leading SAN storage, hands down (of course I will get grief for this, but it's true). EVERY SAN competitor keeps their eye on Netapp, and usually their first words when they try to "sell" -Their- SAN is "WE have a performance similar to Netapp, for somewhat cheaper cost....". That's how they suck you in.. cheaper, cheaper is as cheaper does Smiley Happy

We have Netapp, they are expensive but worth the money. The Clarion from DELL are in some ways equal.. for a lower price point, but it really depends on what you are trying to accomplish.

ALL Enterprise SAN devices that fully support VM Ware will give you what you need, it all comes down to price. You can buy a mercedes or a hyundai, both gets you to the grocery store.. if that's all you want.. it's those long trips to the in laws is where the -ahem- rubber meets the road. . . . . . . . . .

So, planning, strategy, and a good starting point is where you want to be.

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ckboon
Contributor
Contributor

Hi,

What ever the case is, make sure the new SAN & support equipment are:

1) Supported by ESX 3.x (read the docs)

2) Expandable (start small and then grow) by adding more trays or change controller without losing data

3) Get good SAN switches with 16 ports (activate only needed ports)

4) Good vendor support during installation and post sales!

5) Support QoS? I had a problem when a host sucked up all the bandwidth.

6) Ability to replicate to another location for BCP/DR

7) Ability to replicate with another brand of SAN

Also, you need to to think about backup & restore.

Depending on your VM usage pattern, you may want to look at NAS as well. I read that VMware & NAS combo is hotting up.

Have fun!

Regards,

Alan

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rswitzer
Enthusiast
Enthusiast

Right now I have three SANs in different locations. We have to Pillar data SANs and an EMC Clarion. Since I am know SAN expert all I can tell you is what has worked for me so far. I created LUNs 250G. I see that people have bigger LUNs, but so far that size has worked for me. I have around 32 VMs across 6 esx servers and the three SANs. Not a lot right now, but I am still adding VMs to the enviorment.

BTW the Pillar Data SAN cost around $170 for 14T of space.

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