Moving from a Mirror set to RAID 5. How difficult?

[Maritime]

I am currently running Windows NT 4.0 with a two disks (mirrored). I want to add another drive to increase my current disk space. To keep my fault-tolerance up I'm thinking of breaking the mirror and with the addtional drive create a stripe set (Raid 5). To me this already sound stressful. I'm concerned with:
1. Can this be easily done?
2. Will my current Drive lettering be affected?

Any suggestions will be appreciated.
Thanks

 

[Andyleates]

Are you currently using hardware or software mirroring?

Andy Leates MCSE CCNA MCP+I

 

[mbaldwin]

The OS partition must remain on the mirror or single drive since NT cannot operate on a RAID 5 drive. You would have to add a second group of drives (min 3) in a RAID 5 configuration to net more space this way and it would logically become another drive letter on your system.

I'm assuming your using hardware RAID. Using software mirroring (DISK ADMINISTRATOR) would slow you PC down to begin with. Using NT for fault tolerance requires too much overhead, so if your mirror is setup this way, just getting rid of the software based mirror would improve performance.
The bad news is going from software to hardware RAID requires an OS reload.

 

[Maritime]

Unfortunately, I am using Software RAID (Disk Admin in NT).
So based on what Mbaldwin says does this this means that I'll actually have to add 2 more drives? I have two in now,(mirrored) so I'll keep one for the Systam files and the addtional 3 can be configured RAID 5? Am I correct?

 

[NortonES2]

If using software raid I remember from the distant past somewhere that microsoft recommend 64Mb RAM for each 1Gb of disk space on top of memory used by the OS and any other applications.

mbaldwin, we've not had any problems running NT on hardware RAID 5.

-------------------------------

If it doesn't leak oil it must be empty!!

 

[mbaldwin]

Yes it is. Keep in mind RAID 5 is called "stripped set with parity". This gives you the fault tolerance, a stripped set by itself (raid 0) does not. RAID 5 example: if you use 3 2gig drives your net free space is 4gig (one drive is committed to parity). Typically your second drive set will be on its own drive channel.

You can break the mirror and not lose data, but a full backup prior is in order (you never know). I would go with no software raid and good backups instead. Using a hardware RAID controller is much better for fault tolerance & performance. Good luck.

 

[Maritime]

My problem is that I have SqlServer databases running on this server and the config is as follows:

1st Drive - two partitions
C: Operating System and Programs
D: SQL Server Database and log files

2nd Drive a mirror of the first.

If I break the mirror, I'll have to reconfigure SQL to use the addtional space on the new stripe set. However in this senario how is the Operating System Partition protected.

 

[mbaldwin]

The OS will not be protected. If mirroring the OS is important, you could leave the original drives in place and instead of going with a 3 drive Raid 5, add a second pair of mirrored drives (assuming you can't have more that 4 drives total). With this new bigger partition, copy the contents of D: to it and reassign its drive letter to be drive D: & your done.

With that complete, if C: needs to be bigger, your only choice is delete the two partitions (C & the original D) make a new, bigger C partition and a new load of the os, etc.. or use something like Partition Magic.

 

[Maritime]

Thanks a lot for the info.

 

[yizhar]

HI.

Mirror is much more reliable then RAID 5 (remember that with Mirror you have 2 copies and each drive holds a complete copy).
The right solution is to add 2 drives, keep the system OS on the current drives and use the new drives for data.

So in general I agree with what "mbaldwin" wrote above.



Yizhar Hurwitz

http://teachers.sivan.co.il/yizhar