We have recently deployed a small cluster of ESX4 servers (3) that will host some fairly robust SQL servers. These servers obviously need SAS disks. I would like to make use of HA and vMotion and have some questions about it.
I need these servers to have their own arrays and sets of disks. But for vMotion to work I need shared storage. My question is how well does ESX handle shared storage? Will I see any performance hits by letting other hosts see the LUN? Are there any pitfalls here I should be concerned about?
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Well, the first question I have for you is "why" can't you present luns properly.
As for documentation the whole reason for shared storage is for failover/redundancy. In a multiple node environment when running HA and/or vMotion, it is a requirement fo the other nodes to see the guests. Local storage cannot be used for HA or vMotion redundancy configurations.
nappy is right, for vMotion to work you have to have a shared storage either NAS or a SAN.
You can use http://openfiler.com/ to create a cheap NAS solution.
One of my clients had to be PCI Compliant on level 1 which means they had to not only separate their web and sql servers but also completely surrogate their public (local LAN, DMZ) and their processing systems.
As they processed over 800,000 credit card transactions a year and shipped over 7000 packages a day performance was a big part of their concern when moving into such a rule intense and secure system.
From what your saying it seems like have a situation where you are both concerned about redundancy, performance and security.
If you want to truly have high availability solution utilizing VwWare vMotion requires a shared storage.
Also if have a gigabit network between the shared storage and the hosts the performance will not decrease and in some cases will even increase as SQL especially MS SQL will drink RAM as if it was free alcohol in a college party. I've learned that limiting the VM to 2-3GB of RAM and utilizing the /2GB switch upon boot can do a lot for the over performance of windows server 2003 and MS SQL.
If you have specific concerns you should list them.
I was probably not understanding what properly was in this environment until now. Now that you mention vMotion, HA, DRS, etc, it seems like a no-brainer.
What I initially meant was if I have a SQL server that has 3 volumes that need their own arrays on fast disk and one of them only needs to be 60GB, I would be wasting a lot of disk space since 60GB is not very close to the smallest array I can create. At first I was not thinking of shared storage and couldn't see how I would waste expensive high speed disk space once much less 3 times.
Short version is I have put the crack pipe down now and understand. Thanks for the intervention.
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by: nappy_dPosted on 2009-10-30 at 09:19:18ID: 25704449
Shared storage is the best practice and recommended way to go for ESX.
My recommedation is to create a present a LUN specifically to your SQL servers only.
BTW, the more disks you have in your SAN's disk group the better IO will be.