LUN sizing - best practice?

[snootalope]

When we first setup our cluster about two years ago, we were told that we shouldn't create LUN's greater than 500GB. Is this still a recommendation or best practice?

I've got a RAID10 set I'm looking to breakup and make into a couple RIAD5 sets for more space.. something around 750-800GB LUN's. Bad idea?

 

[Provogeek]

it's not the size of the LUN that matters, it's the number of virtual machines that live on that LUN that matter.

The suggestion you got was to help prevent to many VM's from being stored on a single LUN in an effort to prevent disk contention. But if you need to create VM's with larger disk space, there isno problems making a larger lun (2TB is the max, and only one VMFS partition per LUN)

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Brent Schmidt Senior Network Engineer
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[needcoffee]

Some SAN will change the disk block size when the LUN is sized over 500GB. It is important to know what block size your SAN uses based on the provision amount and set VMware to use the same block size when writing data to ensure optimal performance. You should check with your SAN manfacturer or VAR for guidance on sizing restrictions with VMware.

I think for a time most SAN companies were not recommeding using a LUN size greater than 500GB. We have a Compellent SAN (or should I now say Dell) and their best practices updated with ESX 3.5u4 and vSphere. Last I checked they recommended up to 700-900GB per LUN but this may have changed.

needcoffee

 

[mrdenny]

The 500 Gig LUN size limit usually comes from keeping the amount of time to move a LUN around the array shorter, as well as keeping the rebuild time down in the event of a failure.

At least that's why I keep LUN sizes to 500 Gigs.

Denny
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