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Migrate EMC CX3-20 FLARE OS from 10K drives to 15K drives

Our current setup is a EMC Clariion CX3-20 with 4 DAE's

DAE 0 -  15 300GB 10K drives
DAE 1 -  15 146GB 15K drives
DAE 2 -  15 300GB 15K drives
DAE 3 -  15 300GB 15K drives - Brand new in the box, no data

We currently have our FLARE OS (latest version) installed on DAE 0 and wish to relocate the FLARE OS to DAE 3.  At the time of the orginal FLARE installation the only 15K drives that were available were 146GB, however now that the 300GB 15K drives are out we wish to move the FLARE OS to 15K drives for better performance.  The biggest reason for the move is that because our FLARE OS is running on a DAE 0 with only 2Gbps capable the entire SAN is only running at 2Gbps.  It is my understanding that moving the FLARE to DAE 3 will allow the SAN to run at full 4Gbps speed.

Is there an easy way to migrate the FLARE, or do we have to pay to have it done?
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golanego
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golanego
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Duncan MeyersCommented:
>We currently have our FLARE OS (latest version) installed on DAE 0 and wish to relocate the FLARE OS to DAE 3
You can't. If you try, you will break the CX300. Under no circumstances should the FLARE drives be moved.

The CX3-20 has a single back-end loop, so the loop syncs to the lowest speed on the bus - or 2Gb/sec in your case. You can't change this without upgrading to a CX3-40 or higher. The lower back-end loop speed shouldn't be causing you any performance issues at all. Don't forget that the pair of 2Gb/s loops gives you an aggregate bandwicth of 400MB/sec.
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golanegoAuthor Commented:
Understood...but there must be a way to have our cake and eat it to.  For instance if DAE0 blew up how would we recover?   There has to be a way to either migrate the FLARE to a new DAE0 or re-install the FLARE onto a new DAE0.

Thoughts?
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Duncan MeyersCommented:
If DAE 0 goes 'bang' then you are deep in the poo as it includes the Storage Processors, and if they're gone, the box is down. The five OS drives are structured like this:

Drives 0 & 2: mirrored OS for SPA, mirrored secondary OS image for SPB
Drives 1 & 3: mirrored OS for SPB, mirrored secondary OS image for SPA
Drives 0, 1 and 2 - Triple mirrored Persistent Storage Management (PSM) LUN. The PSM carries all configuration information for the array, and is accessed by both SPs constantly
Drives 0 - 4: Vault area (RAID 3) - the dump area for write cache
Drive 4 contains a recovery image and dump areas

So, as you can see, there is loads of redundancy built into the OS drives. In the extremely unlikely event of a loss of the software on the first 4 drives (which I have seen a few times and has *always* been caused by someone moving the OS drives about despite dire warnings. The yellow sticker across the first 5 drives means what it says), EMC carry an OS drive as a spare part from which you can recover the array. You cam also recover the array from the recovery partition and these procedures are well documented within EMC.

In short, yes, you can recover from a situation where you've lost the OS drives, but the chances of it happening via a real fault (as opposed to human error) are as close to zero as you can get.
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Duncan MeyersCommented:
Thanks! Glad I could help.
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golanegoAuthor Commented:
We did find a way in the end.  Replace each 10K drive one at a time with a 15K drive and wait for the RAID to rebuild before moving on to the next drive.  Keep going until all 10K's are replaced with 15K drives.
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Duncan MeyersCommented:
Yes - that's straightforward to replace the OS drives with other drives - but be aware that drive 4 no longer has the recovery image on it. You might want to schedule a call with EMC to have the image installed (it's not a critical image to have present, but if you do need it, it saves time to have it there already).
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