Virtual servers? How and why?

Handruin

Handruin

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With your DAS you're missing out on the vmotion feature that a vmware product can offer. Leave the copy on write snapshots and bussiness continuance LUNs do the hard work for you with scripting of your backups.

Having a vmotion feature also helps with load changes and rebalancing with minimal interaction on your part. You can also make use of pools and shares along with storage IO controls to help with varying loads where you need to prioritize your VMs into tiers, etc. The true hardware community and manageability is really being shown with Ciscos UCS. Pair it into a Vblock with the Acadia VCE config and you can have platform for allocating and reallocating various hardware for different needs. If a piece of hardware dies, everything is handled with profiles so your HBA WWNs and NIC MACs are now all virtualized so changing hardware in a server is easily done once a profile is reapplied to another server. All your LUNs show up and you're connected to the correct network(s).
 
T

time

Storage? I am Storage!
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SAN is just so much more fun because you're putting all your eggs in one basket. I've experienced SAN failures in no less than two corporations; essentially, everyone just goes home for the rest of the day. Even when you have multiple SANs, there always seems to be a key one that everyone relies on.

They also destroy storage I/O performance, but's that's only really an issue with databases.

Having vented, I have to say that Handy is right; Vmotion is very cool. But it's just as flawed a concept as DAS.

Without being able to articulate it clearly, I suspect the future may be in DAS arranged as a SAN - if you see what I mean. Increasingly, we're overflowing with cheap server CPU power; there's no reason you can't embed a massively-multi-core CPU with each LUN, configured for redundancy. Just like Leggo, given 3 or 4 storage size categories, why can't you stack them as required?

In other words, storage-orientated architecture rather than CPU-orientated; after all, this is the 2010's, not the 1960's.
 
Mercutio

Mercutio

Fatwah on Western Digital
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I understand that there's an inherent weakness in virtual database servers, but obviously they're out there and people are dealing with the performance issues of that configuration.

What should I be doing to mitigate the penalties of heavy disk I/O in a virtual environment? Just dedicate some storage hardware on my Host? Make the space available through iSCSI? Or given the size of my customers and what their needs most probably are, should I even worry about it?
 
ddrueding

ddrueding

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1. Don't worry about it.
2. Dedicate a disk.

There isn't that much of a performance hit just running in a virtual environment. The hit is multiple VMs beating on the same disk. Give a VM (or even just the database) it's own spindle (or better yet, SSD) and it will be more than happy.
 
Handruin

Handruin

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Mercutio said:
I understand that there's an inherent weakness in virtual database servers, but obviously they're out there and people are dealing with the performance issues of that configuration.

What should I be doing to mitigate the penalties of heavy disk I/O in a virtual environment? Just dedicate some storage hardware on my Host? Make the space available through iSCSI? Or given the size of my customers and what their needs most probably are, should I even worry about it?
Click to expand...

Why not use local drives to simplify the storage? Put the transaction logs on one spindle (data store) and the database on another just like in a traditional host. Even go so far to put the temp DB on its own if your RDMS has one. I would think iSCSI would give you headaches and performance penalties unless you build a very nice & dedicated iSCSI setup. Unless if you need vmotion capabilities (assuming you're going with a vmware product), I'd stay away from either the SAN or iSCSI for this.

The below assumes again you may be using a vmware ESX product...In addition to storage, you may also want to pay attention to the number of vCPUs you allocate. I've found that 4 vCPU is seldom better than 2vCPU and in many cases 1 vCPU allocation works best. Also make sure to not over-commit memory allocation such that you inadvertently invoke ballooning, compression, or swapping at the ESX level. They'll all cause you to have a bad day with regards to performance. Also try to get the vmware tools installed so that you can use the latest VMXNET3 virtual adapter.

Edit: Also, do not run with snapshots on a data store. They affect performance in a negative way.
 
Mercutio

Mercutio

Fatwah on Western Digital
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Is ESXi 4.1 not free? For the longest time I've just been using the .iso of 3.5 I probably downloaded two years ago.

I went and snagged a copy of 4.1 last night and it's telling me it will only run for 60 days with a trial code.
 
Mercutio

Mercutio

Fatwah on Western Digital
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The fact that there's a (1) on the end of the download file name suggests that it's the same .iso I grabbed last night. What's the 60 days crap about?
 
ddrueding

ddrueding

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IIRC, by default it is a trial of the more advanced version. After you register your free version and type in one of those keys, it makes it the free forever version.

I recommend doing that before creating any VMs that may have features that aren't supported in the free version.
 
B

Bookmage

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You get 60 days to try all the features of ESXi... the free license removes all the paid features like vMotion...

For local computer testing, I use Virtualbox but run a couple free ESXi servers for stuff... :-D
 
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