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SCv3020 and SAS attachments with VMware questions

We are looking at switching from our current HP MSA SAN which is fiber channel to a Dell SCv3020 SAN. I have some questions that maybe someone here can help answer.

We were looking at doing a SAS attachment to three hosts in a ESXi environment (mainly for cost savings). These would be stood up beside our current hosts so we could migrate them one at a time and do testing before full moving and decommissioning of the old servers.

Are there anything we should be aware of with direct SAS attachment compared to our old Fiber Channel setup? Any pros or cons? Our current FC environment is only 8Gbit so moving to 12Gbit is already one plus.

In the deployment document it says VMware vSphere is not supported on servers connected to the storage center over SAS. what exactly does this mean? We current use vSphere in our FC environment, does this mean vSphere running on a server that is attached via SAS or not able to use vSphere at all?

I also was wondering about the RAID levels... I'm a little bit confused, I'm used to RAID0, 1, 5, 6, 10, 5+0, 6+0 etc... Dell calls it RAID 5-5, RAID 5-9, 6-6, 6-10 what is different about these? Do I have to have a RAID array with a fixed number of disks? Like RAID5 must have 5 or 9 disks? Can someone clear this up for me.

Replication wise, we were thinking about adding another SCv3020 at some point and replicating it via iSCSI to an off site location. Are there any issues with having direct attached SAS setups then using iSCSI for replication?

We are also wanting to have encrypted storage, obviously we need an encryption license and self encrypting drives.. is there any pros or cons to doing this at the hardware level as opposed to doing it at the ESX level with encrypted virtual drives?

As for ESX hosts, when they are attached via SAS how does a VM failover work? With Fiber channel its pretty much seamless since everyone on the fabric can be set up to see the LUNs.. how do you handle this with SAS or can you?

 

Thanks

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Origin3k
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Re: SCv3020 and SAS attachments with VMware questions

In the past 6-7 years we setup around 30-40 of these SAS storage system starting with PowerVault MD3 (32xx, 34xx) and than moving to SCv2020,3020 and even 5020 for customer who never have a need for more than 4 Hosts.  vSphere supports this kind of setups[1] for ages now.

Yes the 12G is slighly more than 8G FC and also lower latency.

Also on a modern SAS storage the LUNs are mapped to all connected Hosts so vMotion ,HA are working as expected. There is no different compared to FC or iSCSI and the way how to configure is the same and on SC its named "mapping".

Yes we use async. replication with SCv2020 and 5020 and both are running on SAS. A SAS version never can use sync. replication or live volume. Keep also in mind than RIRA licenses are needed and when speaking about 3020/5020 you need the mezz. card options because there are no dedicated Repl. ports anymore (like on SCv2020).

I think that we never go for the encryp. options because of the limited drive options. Also mixing encryp. and standard drives is not supportet. So think about if you would go this way.

 

A SC will try to write a stripe over 5 or 9 disks so this is why its called Raid5.5 or 5.9. The later one gives better space efficiency. If you select Double Redundancy (allows up to survive 2 disk failures at once)  than the system use RAID6 with stripes over 6 or 10 disks.

The SC dont use fixed diskgroups like older  storage systems. Instead it groups "similar" diskstypes into diskfolders (like a pool) and every volume(LUN) can use a different policy which can change as often and when ever you want.  Also the SC used dyn. RAID level with RAID tiering based on the policy it starts with RAID10 and converts than to RAID5/6 with the option to migrate data (data progression) from Tier1 over Tier2 into Tier3.

[1] right now there is no way that a vSphere 6.5/7 together with a SAS SC works out of the box. The right driver needs to select manually and also a special command line option needs to be set.  Yes, they have  updated their vSphere Bestpractices guide a couple of weeks ago. But we had a hard time in the past months.

 

We and our customers like the SC with SAS!

 

Regards
Joerg

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BSH-RESCH
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Re: SCv3020 and SAS attachments with VMware questions

Thanks for the information!

 

So is the SCv3020 a compellant or EMC solution? I can't find it on the vmware comparability list but I can find compellant storage center and I can find EMC similar sounding products

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Origin3k
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Re: SCv3020 and SAS attachments with VMware questions

Hehehhehe..... right now the company is DellEMC and maybe in the near Feature Dell Technology.   DellEMC renamed the brand "Compellent" to  "SC" (StorageCenter) a long time ago. Dell bought Compellent in early 2011 and with the launch of Compellent SC8000 and SC4020 or shortly after they renamed Compellent to SC. Our SC220 bezels are labeld with Compellent Smiley Happy

So for the VMware HCL select both Dell and DellEMC as company name and search for the term "Center". You will see different entries based on frontend connectivity like FC, iSCSI and SAS.  They always certified a Storage Center OS Version like 6.6, 7.2,7.3 rather than a modells like SCv2020 or SCv3020. So when SCOS7.3 is available on SCv3020 than its good for vSphere.

 

Regards
Joerg

 

 

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BSH-RESCH
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Re: SCv3020 and SAS attachments with VMware questions

Ah, now I see what I am looking for..

 

btw. You said vSphere works with SAS, we're still tripping over the fact that the deployment guide said vSphere is not supported with SAS attachment. 

Do you have any documents that you know of that show this deployment setup with vSphere or articles that show how to configure it? I now the SAS driver issue is one of the big problems, which is easily fixed. We just need some documentation to back up that it works before we make this move.. after many years of fiber channel this is a new path for us.

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Origin3k
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Re: SCv3020 and SAS attachments with VMware questions

Just take a look into VMware HCL for Storage Center SAS

Right now the latest best practice Guide https://downloads.dell.com/manuals/all-products/esuprt_solutions_int/esuprt_solutions_int_solutions_...

Take a look to chapter 6.12 and D1.

 

How to setup a SAS SC for VMware
https://downloads.dell.com/solutions/storage-solution-resources/VMware-with-SAS-FE%20Solutions-Guide...

 

The question about the right driver

https://www.dell.com/support/article/de/de/debsdt1/how11081/preparing-vmware-esxi-hosts-to-attach-to...

and the new setting for vSphere 6.7
https://kb.vmware.com/s/article/67006 together with 4.2.3 from the BP Guide.

 

Regards
Joerg

 

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BSH-RESCH
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Re: SCv3020 and SAS attachments with VMware questions

Thank you! This is a big help

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Re: SCv3020 and SAS attachments with VMware questions

Test

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BSH-RESCH
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Re: SCv3020 and SAS attachments with VMware questions

We have a HP cluster node what is going into this new cluster, we aren't 100% switched over to Dell yet... it's been a long process...

Is there any compatibility issues with using a HP 12Gbit SAS dual port card with this SAN? I believe it's just a re-branded LSI SAS 9300-8e SGL.. being SAS it should be able to talk since it's a standard even if it has custom HP firmware on the SAS card right?

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Origin3k
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Re: SCv3020 and SAS attachments with VMware questions

You will not find a single paper which showing that connecting a SC SAS to  non dell PowerEdge 13/14. Gen together with the Dell 12G SAS HBA is supportet. Sorry.

Will it work? Most likely yes! But nobody will gurantee.

We have connceted a SC5020 against 2 4x CPU Socket HPE Proliants with HP 12G SAS HBAs without trouble. Customer switch 6 month later to 4 R740 because the HPE runs out of support.

We have connceted a SCv2020 against Fujitsu RX Server with their 12G SAS HBAs.

We have connected a SCv2020 against Whitebox Server by using Dell 12G SAS HBAs.

So when ever possible we use the Major Server Vendors and there 12G SAS HBAs because outerwise you will unable to monitor and upgrade FW to that devices.

 

But if possible you should avoid this kind of setup.

 

Regards
Joerg

 

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