Migrate RAID and Expand

[nevets2001uk]

We have a Windows 2003 server currently running on 4 physical 146GB SCSI disks.

These are split into 3 Logical Disks at RAID 1+0 and each has been assigned a drive letter in Windows C, D, E. The split is Logical 1 = 20GB, Logical 2 = 130Gb and Logical 3 = 130Gb. The controller is a Smart Array 641 Controller.

We are running a bit low on space on the last two logical volumes and would like to reorganise the configuration and add some disks to improve the situation. My proposal is to add two extra 146Gb disks and to change to RAID 5 for the whole system.

I wanted to run my planned procedure past you to get an idea if it should work as expected. We would like to ensure no data loss during the process (although will have a backup on standby).

1) Full System Backup (Maybe ASR)
2) Add the two new disks and expand the array
3) Convert the logical volumes to RAID 5 using the Migrate RAID option on one logical at a time
4) Once complete the additional space should show in Windows. Can we then expand the partitions D and E to utilise the extra space?

Does this sound sensible?

Steve G (MCSE / MCSA:Messaging)

 

[TechCoordinator]

I have been researching expanding (SMARTarray w/641 controller) my 3-drive RAID 5 to a 6-drive RAID 5 and have found out that you lose one drive to the parity being striped. That would give you 146GB * 5=830GB of total space after having a total of 6 drives.
But I am not sure that you can do this one logical drive at a time. I believe you would partition the array and then assign the volumes, which you could assign the drive letters to.
In other words, I think that the partitioning is done at the hardware level, not the logical drive level.
I do not mind being corrected on any of this because I have not completed my reconfiguration yet. Best to you.

 

[cajuntank]

You can add the drives and expand the existing array, but with RAID1+0 you have a two drive "penalty", so having 6x146GB drives gives you a total raw space of 584GB of drive space. This you can easily do by adding the additional drives, expanding them into your existing array through the HP array configuration utility and this can run while system is in use and online, and then use something like partition magic or some software to expand existing partitions to use the now free space that you have.

Now if you want to change your array over to a RAID5, you will have to completely destroy your existing array to re-create it as a RAID5 in which you would have raw space of 730GB or 584GB if you configured with an online spare. Doing this scenario would require Ghost, Acronis, or some imaging software to image off the partitions so you can re-create and image back.

Before doing either one, make sure you have some form of total backup of the system, preferably a image of the box in it's entirety in case crap happens. I would personally keep the RAID1+0 since it's the less "destructive" of the two scenarios and you get better fault tolerance/availability, better random write performance, and better sequential read and write performance.

But hey, that's my two cents and it don't buy much.

 

[nevets2001uk]

Thanks for the suggestions so far. My only query now is that the RIAD migrate option within the Array Configuration utility suggests that it can change the RAID type non-destructively. Is this not the case?

Steve G (MCSE / MCSA:Messaging)

 

[cajuntank]

New one on me if it can change RAID types non-destructively.
If it can, this must be something new in the firmware.

 

[nevets2001uk]

This is Array Config Utility 7.40.8.0

Under the wizard the option is called Migrate a Logical Drive - Change the RAID or stripe size of an existing logical drive without disturbing the data on the logical drive.

Steve G (MCSE / MCSA:Messaging)

 

[cajuntank]

Looks like your right (learn something new everyday). I looked at mine and saw what your seeing about migrating to another RAID level. Of course, I've never done it, I have expanded an existing array (same RAID level) a few times, but never migrated one. I would trust HP to do it without issue more than I would Dell, but this is one you might want to call HP tech support on to make sure about firmware and drivers so that there's no hiccups in the middle. My ACU was ver 8.x so your a few rev's back. Good luck.

 

[spi200]

Hi

You can migrate from some Raid levels to another type without losing data, it just can be done in every combination. The good thing is the ACU will assist you and will not let you migrate to a RAID level that is impossible and it will warn you if you are going to loose data.
I have done simple expansions from RAID1 to RAID5 without problems, not sure about RAID10 to RAID5. We used RAID 5 for years and often had performance issues and disk contention, now we use RAID1+0 (RAID10) and we would never go back to RAID 5 for a production system. Disks and controllers are cheap so it may be an option to buy an external storage device or maybe just add two drives in a RAID1 setup and just use it for Log files or the Server swap file etc. ie No data which is critical.
Which ever way you go you can extend your partitions with Windows 2003 SP2 faily easily, just ca not do any volume which has a swap file and can not do the system partition. The swap file of course can be moved around to another volume while you extend it and then move it back. Some after market products will allow you to Extend your partitions and volumes graphically rather than command line.

Good luck

Dave

 

[TheLad]

Just make sure you have a successful backup prior to starting any work of this nature, better to be safe than sorry

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