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HP Storevirtual 4330 3 nodes network raid selection

shang83
Occasional Contributor

HP Storevirtual 4330 3 nodes network raid selection

Hi,

 

Here's my scenario, currently my environment are using 2 nodes of HP Storevirtual 4330 configured as network raid 10 and the volume are all thick provision. The purpose of the storage are for Vmware Virtual machines.

 

Recently a new node been purchase and added to the cluster. My management wanted to changed the existing volume data protection from network raid 10 to network raid 5 to reduce the volume consume space.

 

I read the user guide, network raid 10 are the best network protection for virtual machines performance. If the network raid protection changes to network raid 5, are there much impact to the performance?

 

About the network raid 5 single parity, how it really protects the data? Now that I have 3 nodes, If one node fails does the data still available? I read the user guide and it seems to stated that the data would still be available.

 

I'm quite confuse on the parity thing.

 

Thanks in advance

 

 

P.S. This thread has been moved from Storage Area Networks (SAN) (Enterprise) to HP StoreVirtual Storage / LeftHand. - Hp Forum Moderator

 

 

4 REPLIES
Dennis Handly
Acclaimed Contributor

Re: HP Storevirtual 4330 3 nodes network RAID selection

>About the network raid 5 single parity, how it really protects the data?

 

At least for drives, if you have RAID 5, you can compute the data from the remaining N - 1 drives by using XOR.

 

>I'm quite confused on the parity thing.

 

For RAID 1, you just have copies.

For RAID 5, you have an extra parity disk that's an XOR of the others.

For RAID 6, you have two extra parity disks that uses a complex XOR of the others.

 

Bart_Heungens
Honored Contributor

Re: HP Storevirtual 4330 3 nodes network raid selection

Hi,

 

For a detailed explanation on how Network RAID really works check out my blog post on it: http://www.bitcon.be/?p=2537

 

So yes you will survive with Network RAID 5 a node failure...

 

However HP recommends to use network RAID 5 only in read-only environments like achiving and so... Let's say network RAID 5 is not the most performant solution in heavy write environments... When you buy StoreVirtual, you choose forhigh availability in some kind of way, so always go for network RAID 10...

 

 

Kr,
Bart

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oikjn
Honored Contributor

Re: HP Storevirtual 4330 3 nodes network raid selection

++bart.  NR5 is really for archive data only.  I would NOT use it for VMWare data stores.

 

Why are you running thick provisioning?  It generally isn't needed.  Even for volumes I know will expand 100% I still make them thin so the snapshots will also be thin.

 

Short of slight overprovisioning with Thin volumes, your space usage is what it is.  Volumes really must be NR10.  If you need more space, you just have to bite the bullet and buy another node or move data you don't need on the SAN off to something else, but keep in mind, the net usable space you get when you add one node is effectively 1/2 of its rated capacity since all data should be NR10  (also keep in mind that you really only get as much usable space as your smallest node, so if you have 7TB nodes, buying a 14TB node won't get you 14TB space when you add it to the cluster.

shang83
Occasional Contributor

Re: HP Storevirtual 4330 3 nodes network raid selection

Sorry for the late reply. Thank you for the feedback. My management agree to stick with raid 10. If I not mistaken, does the volume provision able to change from thick to thin live?