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Loss of Data?

Posted on 2010-08-29
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Last Modified: 2012-05-10
Have an LSI MEGA RAID SAS 8308ELP Raid Controller with MegaRaid Storage Manager v. 2.30.00 on a Windows Storager Server 2003 Service Pack 2 Gateway Server. I am wanting to add one (already 4) SATA hard drive to a Raid 5 Array and keeping the same raid configuration on one enclosure. I also want to add 3 more SAS drives to another enclosure with 2 existing hard drives and change the Raid configuration to a Raid 6.   I am unable to back all of the data from the all of the physical drives.  
Question.  Is there a good chance that reconstructing the virutal drives going to wipe out my data on the existing drives?    
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Question by:Van Johnson
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Casey Weaver earned 250 total points
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The 8308 supports Online RAID Level Migration. and Online Capacity Expansion. I use one myself. Do just one task at a time to minimize the time the system is in a critical/vulnerable state. Handle the OS drives first if you have one, then the data drives. I've done move OLM and OCE. I went from a 500GB x 4 RAID 5 to a 2TB x 8 RAID 10 . First step was to use OCE to go from the 500 array to the 2TB's one drive at a time. After that I installed the second enclosure with the 4 more 2TB's and did OLM to RAID 10. This was slow and between work and all the two steps took about a week. It'll be much faster if you can take the system down and do the upgrades directly from firmware where the drives won't be under use as the array builds/rebuilds.

There's *always* a chance of data loss, but you *should* be safe. The card is designed to do this job. But there's always a flub. Make sure your card has a BBU and/or the server is on a battery backup that can last a typical outage, you really don't want to loose power without one of those going (most likely will kill your array), and if you can help it, you always want power going to the server.
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The controller supports online expansion, so yes you can do it.  Best practices include:
1. Making sure firmware, BIOS, drivers are all current (then do full power cycle)
2. Do data consistency check First (yes I know this takes time, but in event you have some disks with a lot of bad blocks, this cleans them up .. and if it can't clean them up, then it will trigger the hot spare rebuild).  So better to clean up any messes now.
3. Battery backup for controller HIGHLY recommended.  In event of power loss, or multiple simultaneous media errors, the BBU will prevent data loss.   It will also run much faster.  W/o it, it could add several days to the process.
4. make sure you back up (sorry, but this is best practices.  Odds are extremely low there will be a problem, but it is just plain wrong not to have a backup).   Don't forget, your operating system could always have some issue once the LUN(s) are resized.  The RAID controller won't care about such things as it is O/S agnostic.
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by:Van Johnson
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Thanks for the tips
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