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Equallogic Mirror
Hi,
I actually very new to Equallogic and just supplied 2unit of Dell Equallogic PS4110E with 6x3TB HDDs to a customer.
For some reason, they are not confident of the reliability of the product. I have tried to convince them accordingly but they just don't buy it. Seems that they got burned on some other 3-letter vendor SAN and now nothing is totally reliable.
Anyways, they want to configure the 2 units as follows:
1. Both units as RAID5 across 6disks.
2. "Mirror" the 2 units.
3. Have single point access to the SAN from their VMWare farm.
The base worry appears to be that after one entire unit fails, they will still be able to transparently access the data. Some sort of a RAID51 configuration. The system will expose a single LUN to be mounted in the VMWare farm and then sliced and diced there as necessary.
I've been trying to get hold of manuals for the units but can't seem to find them. I got the customer to register for a support account but after 2weeks it seems their account is still pending approval.
This appears to be a replication-based setup but I can't see how the two replication partners can be addressed as using a single virtual IP.
Any pointers from anybody will be extremely helpful!
Thanks.
Daniel
DELL-Joe S
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October 25th, 2012 08:00
Item 1: When setting the RAID policy for a array member, you cannot select specific drives, the policy is for the whole member and includes all the disks in that member.
Item 2: if both arrays are setup in the same group, you can put each member in a separate pool and use the SyncRep feature to mirror the volumes (not the whole array). Or, if the two members are setup in different groups, you can use replication to replicate the volumes to a DR site.
Item 3: Yes this is possible, you need to properly configure the VMware system for this, the links below explain how to do this.
The documents for configuring the array, switches, and servers are here: en.community.dell.com/.../3615.rapid-equallogic-configuration-portal-by-sis.aspx
You also want to review the configuration guide (this is a quick over view of everything needed to create a EqualLogic iSCSI SAN): http://en.community.dell.com/techcenter/storage/w/wiki/2639.equallogic-configuration-guide.aspx
There are also several public documents here:
http://en.community.dell.com/techcenter/storage/w/wiki/2632.storage-infrastructure-and-solutions-team-publications.aspx
Regarding the support site access, the customer should contact: Eqlx-customer-service@dell.com to expedite the web site access.
-joe
DELL-Joe S
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October 26th, 2012 07:00
Q1: Dell has some export (and re-export) restrictions on what can be published externally (publicly) and what is available only to customers that have registered EqualLogic arrays. These restrictions are why you see some differences between (for example) a switch and what is available for EqualLogic. However, provided that your EqualLogic Service Tag (ST) is registered with Dell, you can always call the support number, and they can send you any documents you need (support.dell.com/.../equal_logic)
Q2: Physical location is typically not an issue, what is important is that all member of a group be on the same iSCSI subnet, which appears to be exactly what you have. Creating a new pool in the group and moving one of the members to the pool is a strait forward and simple operation. You can see the steps and how to do this on the online help at (Firmware v6 used for example): psonlinehelp.equallogic.com/.../groupmanager.htm. This link is also available from within the Group Admin GUI, just select the "?" icon.
Just search for “moving member”, or how to “create a new pool”
Q3: Yes, I was referring to Synchronous Replication; this requires that all members in the group are on the latest version of the v6.x Firmware. About using Internet search engines to find EqualLogic information; only information on the Dell TechCenter, or the public equallogic.com site will be listed, items that require a support contract will not show up.
Q4: SyncRep information is here: www.dellstorage.com/.../DownloadAsset.aspx
Q5: MEM has no bearing on SyncRep, and is not needed. It is an optional tool that you can use for a more simplified way to configure vSphere/ESX for multipathing. When you get your login, you should also check out the new “Virtual Storage Manager for VMware” this is in EPA (Early Production Access), and will replace the HIT/VE (Host Integration Tools for VMware).
For VMware typically the best configuration for the EqualLogic array is:
1.) Delayed ACK DISABLED
2.) Large Receive Offload DISABLED
3.) Make sure they are using either VMware Round Robin (with IOs per path changed to 3), or preferably MEM 1.1.0 (or higher).
4.) If they have multiple VMDKs (or RDMs) in their VM, each of them (up to 4) needs its own Virtual SCSI adapter.
5.) Update to latest build of ESX, to get latest NIC drivers.
6.) Too few volumes for the number of VMs they have
Finally, we try to do our best on the forum’s to answer your questions, however, the one thing we ask is that you try to limit the question to one topic (whenever possible). This makes it easier for other forum users to follow along, and hopefully find useful to them as well.
-joe
DanielLSB
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October 25th, 2012 23:00
Dear Joe,
1. Thanks for the pointer to Equallogic Support. Seems that even after merging for so long, Equallogic is still operating as an independent business line within Dell. :) I have emailed them accordingly about the support account.
2. In this case, the two units are in the same group and I can configure them into two storage pools. The two units are physically on top of each other, connected to the same network switches (Dell 8024) directly via 10G Copper Ethernet.
3. I assume that you are referring to Synchronous Replication when referring to SyncRep. This is a fairly new feature and I have very limited information on this. Is there anywhere I can get access to the actual manuals for the PS-series without access to the support website? Its quite urgent and I don't really have the time to wait for the Dell Eql support team to revert. I've tried googling but there seems to be nowhere which I can download the actual manual. Config notes yes, somehow manuals no. :(
4. Looking in detail at the configuration document you referred to, it seems that SyncRep is EXACTLY what I want/need. :) However, they do indicates that a failure will cause interruption to the iSCSI traffic and the VMWare servers will have to reconnect just without reconfiguration of the iSCSI initiator. I do admit that this is extremely unlikely since we specified Enterprise Storage for the uptime. But realistically what will be the impact of a total chassis failure in the above scenerio, ie. 2 units with 1 volume SyncRep-ed across? Do I have to configure a longer timeout on the VMWare for the iSCSI initiator? Sorry to ask what may be a stupid question but the config docs do not address it.
5. The VMWare config guide only details the process for installing the MEM modules for VMWare. Or does the MEM assist the VMWare Host to handle the SyncRep member failover/failback? In which case, to acheive this cleanly, the MEM is a must. Currently the MEM has not been installed since I don't actually have the plugin without access to the support website.
Thanks for the assistance! I greatly appreciate this.
Daniel
DanielLSB
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October 26th, 2012 09:00
Thanks a million Joe. You've been extremely helpful.
1. Noted on the large number of issues on a single thread. I will try to avoid this in the future. BTW, Dell Eql-support just replied me to expedite the account creation so that issue is resolved.
2. I was on this forum elsewhere and was told (by your colleague from Dell Don) that the failover for SyncRep is currently not automatic in the event of failure and that this automatic failover feature is planned for a future release. Is this a confirm feature and if so, what is the timeline to feature release?
Daniel
DELL-Joe S
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October 29th, 2012 09:00
As indicated by Don, no specific time line can be discussed in a public forum. If you contact your Sales team, they can get a NDA (non-disclosure agreement) setup with you, and then they can discuss new features and expected time that it will be available.
-joe