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Migrating RAID arrays between Dell PowerEdge servers

We're planning some DR scenarios and one of the things I need to understand is the limits / options for recovering data from RAID 1 arrays where the original server has died. The original server is set up with 2 RAID 1 arrays O/S and data. What I want to do is take the Data array (either as a set or one of the 2 mirrored disks) and see / access the data on the disk from another server.
I need to understand if this is possible on the following servers

 Dell 2500 (Perc3/Di) to Dell 2500
 Dell 2500 to Dell 2600
 Dell 2500 to Dell 2850
 Dell 2600 (Perc4/Di) to Dell 2600
 Dell 2600 to Dell 2850
 Dell 2850 (Perc4/Di) to Dell 2850

From reading around the forums it appears that this is only possible on the Dell 2500 boxes if the new server (recipient) has the same model and firmware of array controller as the old server (donor) due to LUN roaming not being insttalled on the 3/Di card, however I'm really hoping that someone out there can tell me otherwise.

This could cause me a lot of work and pain if I get it wrong so 500 points up for grabs

Any ideas?
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NacMacFeegle
Asked:
NacMacFeegle
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3 Solutions
 
mcp_jonCommented:
The easiest way to do it is, in case of a failure, take one Mirror disk out, and insert in one of the other Poweredges, then go into the Controller's Bios and create a new container using the Disk information.

Try to place the other Mirror disk and Boot Normally !

Perc should be Retrocompatible :)

Best Regards !
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gurutcCommented:
Well, the first thing to do is to make sure you have a good backup!!!  

We move arrays from 2600/2650 series to 2800/2850 series back and forth all the time with no issues.  The 2500 to a higher revision could be touchy and this has worked for us sometimes and sometimes not.  It's almost a 'hold your tongue right' thing.   So...  although I can't absolutely answer the 2500 to other series part of this, I can tell you that the other moves should work.  But every one of these scenarios is doomed to failure by Murphy's Law if you don't have a good backup.  Just looking hard at a drive with your eyes kills it around here if there's no backup.

Good Luck,
Travis
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mcp_jonCommented:
Well said, Travis !!

Backup, the Magic and most Forgotten world in IT Industry !

Best Regards !
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gurutcCommented:
Thx mcp_jon.  Our peer-pressure induced backups should make things go just fine for the author!

- travis
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NacMacFeegleAuthor Commented:
Guys thanks for this I'll take a look on the test system with particulr regards to mcp_jon's method of creating the container first - can you create a RAID 1 container with only 1 disk?
The whole area of data backups is difficult as these servers are used for dynamic storage of images prior to processing (data only there for 12 hours) and passing across to downstream mainframes. We process several million images in 24 hours so backups are not really possible. Currently if a server goes down the recovery action is to recapture the source data and repopulate the directory. What I'm trying to do is 'rescue' the data on the array and access it from a separate server.
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gurutcCommented:
Ok, well the best plan for disaster recovery is going to be having an exact duplicate of the server ready to go that you can plug the drives right in.  That would work every time.  So... what's all your time worth trying to figure out if a similar server will do the trick?  And what's it worth not knowing for sure?  Is your job on the line?  If so, demand a duplicate server, available and ready for use, in the event that the primary box goes down.  Also, there are hundreds of data mirroring apps and solutions out there that don't require the complexity of clustering.  You could just hook up some fast external USB drives for instance and do scheduled updates of the changed contents to them from the array - just in case - using commercial real time backup software.  Or better you could do this using Open Source such as RSYNC, which I use for real-time replication of 2 Terabytes of changing data 24/7.

- Travis
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mcp_jonCommented:
" Guys thanks for this I'll take a look on the test system with particulr regards to mcp_jon's method of creating the container first - can you create a RAID 1 container with only 1 disk? "

No, must have at least " two ". When I said to place only one was for the Perc Controller to read the Info from it, and in case you do something wrong, you could always recover it inserting it  back on the Original System !

Best Regards !
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NacMacFeegleAuthor Commented:
Travis,
we're looking at putting in hot standby boxes. One of the challenges is that there are over 30 servers doing this function in different sites on different Dell hardware. The majority of them are Dell 2500 which is why I need to know if I can transfer data in a RAID array from a 2500 to a 2850 where the 2850 will be a new hot spare box with OS installed. We're looking at buying up to 10 new servers purely as standby boxes but I obviously need to know that it'll work before committing ~£20K on hardware. The backup option has been explored but just doesn't stand up in terms of access and the transience of the data on this node. I'm looking at gettting it backed up earlier in the cycle if possible at the point of capture.
I'll let you know how it goes with the disk migration.
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NacMacFeegleAuthor Commented:
mcp_jon,
sorry if I'm being a bit thick here. If server 'A' has the 2 data disks in RAID 1 then how many do I put in Server 'B'? Once they're in there how do I import these disks as a RAID 1 set? Once the disks go into server B it doesn't see them as a RAID array so do I create the array but not initialise the drives?
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gurutcCommented:
Ok, I see your dilemna.  One thing you'll have to deal with is that the Array Drive Holders are different between the 2500 series and the 2600/2800 series servers.  To move the drives to the newer boxes you'll need to unscrew them from the 2500 drive holders and remount them in the newer holders.  This is not without danger to the drives and they could be damaged.  Also, it is a real bear (speaking from experience) to keep the drives in order when doing this.

Travis
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gurutcCommented:
Ok, here's what I'd do.  Buy some Powervault Array Enclosures.  Move the drives to the enclosures.  Then get the Plug-in array controller, not the on-board one, for each server, this way the RAID controller is the same no matter what box it is in.  Then if a server croaks, you just move the array cable to another server and bingo, you're working.  This should be in the same ballpark as buying a pile of new servers cost-wise and should be a lot more reliable solution since it doesn't involve re-creating arrays or physical disassembly of any components.

- Travis
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NacMacFeegleAuthor Commented:
Gurutc,
powervault eclosures would have been a good way to go originally but I'd now be looking at buying 30 of them which is going to be a lot more expenive than 10 new 2850's also they'l need a whole load of additional rackspace so it's not an attractive retrofit option. I'm still working on having the recipient 2600 server sitting with 2 raid  arrays in it (OS and data). Then take the data array out and replace it with the data array from the 2500 server. I've had info back from Dell here (http://forums.us.dell.com/supportforums/board/message?board.id=pes_hardrive&message.id=22178) that says because the 2500 and 2600 RAID controllers are different chipsets that its unlikely that it will ever work but I need to prove it out for myself to the bitter end.
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mcp_jonCommented:
No problem about "thickness" . . . :)

By reading the Data on the disk, the controller will know that it is part of an Array, Raid 1, and Will import those definitions !

Best Regards !
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Dell100Commented:
Dell 2500 (Perc3/Di) to Dell 2500  can do it
 Dell 2500 to Dell 2600 Wont work
 Dell 2500 to Dell 2850 Wont work
 Dell 2600 (Perc4/Di) to Dell 2600 can do it
 Dell 2600 to Dell 2850 can do it
 Dell 2850 (Perc4/Di) to Dell 2850 can do it

Most of these you will be fine moving disks between. 9/10 times you can move disks between similar controllers e.g. PERC3 to PERC3 and PERC4 to PERC4. Some important diffrences

Embedded PERC controllers (with I as the last letter e.g. PERC 3 D/I)

Any PERC X X/I cards before PERC 3, are all adaptec based cards. You can swap HDD's between these cards with no issues or data loss.
Any PERC X X/I cards that are PERC 4 and above, are all LSI based cards. Any HDD's created in a PERC 3 D/I,PERC 2 D/I, PERC 2 S/I will NOT work in a PERC 4 D/I, and vice versa.

PCI/PCI-E cards

All PCI based cards (Denoted as PERC X X/C) are LSI based (except PERC 2 Q/C card which was Adaptec) and will work fine with any PERC X X/C cards are any PERC 4 X/I  embedded solutions.
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Dell100Commented:
Sorry, forgot to include that you would need to pull the config from the HDD's when moving them.

Poweredge 2500 has a PERC 3DI
Poweredge 2600 has a PERC 4DI
Poweredge 2800/2850 has a PERC 4DI or PERC 4 eDI card

2600 and 2800/2850 cards are compatible, but the 2500 is not !
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gurutcCommented:
OK, leaving out the the issues with swapping the drive holders, just do this:  Get an identical non-embedded array controller, ie PCI card, for all your old and new servers.

Travis
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Dell100Commented:
Better yes, buy a Powervault 210/220 .  The drive holders from the x6xx gen servers will work with x8xx gen servers, but you would need to swap the holders for the x5xx server
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Dell100Commented:
But yes, buying a PERC 4 DC controller and running you server off it, you should be able to migrate that to you disaster server if needed.
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NacMacFeegleAuthor Commented:
OK going to go with Dell100 answer as that matches the 'official' answer from Dell (came in today) and matches my testing. Thanks for the suggestions re PowerVault and external drives but the original question was whether or not the drive migration would work.
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DRnkcCommented:
The easiest way to analyze a Dell RAID controller migration is by the type of controllers.  

If it's an Adaptec controller (Ctrl+A for config) you can pretty much move disks around all day between servers and shared controllers on the same server (even spanning disks across shared controllers). Adaptech writs the disk config to the disks and stores it in BIOS config...

AMI (Megatrends) controllers (Ctrl+M for config) are much pickier (IMHO) they obviously write some sort of config to the disk as I've moved mirrors between controllers but trying to share configured disks between (multiple) controllers and sometimes even just moving them between channels on the same controller but getting the order wrong can end up with issues...

The best bet - keep a ghost (or other) image of the server on hand with a network boot CD/USB and have a pre-existing case open with Dell for the migration.
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mcp_jonCommented:
Hi DRNKC,

Why bother to use Ghost if this can all be easilly done on a "Hardware" basis :) ?

Like, create a mirror and take one disk out. That disk that you have taken can be the "master" disk for any new server that you will create.
Or perform a syspreped image and reuse it :)

Best Regards !
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