Mirroring a server

Question

I want to mirror our PowerEdge 1800 Windows Small Business Server 2003.  Can someone tell me if I need to purchase an operating system or other software for the 'mirror', or will the original server 'build' everything to the new redundant server?  Is there existing software on my current server to do this automatically, or how do I set up the source server to mirror itself to the new server.  Do the two servers need to be located close to one another, or physically connected to one another, or is a network connection all that is needed?  Thanks for any help you can give.

jmwills · Answer

I don't think you can mirror an SBS box since it can be the only DC on the LAN.

troedel · Answer

jmwills,

Thanks for your response. Since you said you don't think it can be done, is there anyway I can verify if that is true. There are 8 owners of my company that I need to convince that this cannot be done. I always have to make sure my information is correct before I present it to them. What other suggestions are there for securing a server from causing downtime in case of mechanical failure?

troedel

Bill Lally · Answer

Depends on what you're REALLY trying to do.

If you are truly attempting to mirror the server, then you will be talking about clusters. And this will take you to the high-end of the Windows Server Operating Systems (if you're using Windows).

If however you are talking about mirroring of the server's hard drive, well then you just need a second identical SCSI hard disk and the array manager that comes included either with Windows Server 2003 Standard or Windows 2000 or your Dell IT Assistant software. Use the Array Manager to create a RAID1 SCSi mirror (I'm assuming SCSI; I'm not sure what you can or can't do with SATA drives as I've never used them)

Hope this helps and good luck!

troedel · Answer

Bill,

Thank you for your response. We have the SATA drives and not SCSI. We are having a hard time finding out if you can indeed mirror a Windows Small Business Server system. We have been told you cannot have two SBS systems on the same LAN. If this is true, how do you achieve the redundancy needed for a rebuild after a hardware failure? If you rely on RAID to rebuild, you loose at least a day of work. The same holds true with restoring a backup. If the failure occures before the backup has had a chance to run, you have lost a days worth of work that cannot be recovered without redoing everything. Any suggestions?

Trena

Bill Lally · Answer

Talking about redundancy of the drives only (and nothing else) . . .

SCSI drives in a RAID 1 or RAID 5 (my preference) hooked up to a PERC (PowerEdge Raid Controller) is probably the way you'll want to go.

A PERC can have 4 or more drives attached. 3 or more drives will form your RAID 5 Logical Drive. Only 2 of the 3 drives will actually provide disk space; the 3rd drive provides a parity check for the RAID 5 striping. This way if one of the 3 goes bad, the RAID Controller can rebuild the Logical Partition on the fly using only the other 2 drives and the 4th drive (called a Hot Swap drive).

So, let's say that you had a PowerEdge Server using a PERC 4e card along with 4-73 GB 15K RPM SCSI drives (all drives should be identical in RPM speed and must be identical in Hard Disk size).

Your Windows System would actually "see" approximately 140 GB of available space for your C:\ and D:\ drives.

Disk 1 & 2 provides (+/-) 140 GB of disk space. 73 GB X 2 = 146 GB minus a few Gigabytes of lost space during Logical Drive formation.

Disk 3 is a drive which is not seen by the Windows system but is used by your PERC 4e card to provide RAID parity checks

Disk 4 is also a drive not seen by Windows, and sits idle and online "just in case" the PERC 4e card calls upon it to take the place of another disk drive which has gone bad.

Hope this helps!

jmwills · Answer

I do know for a fact that an SBS box can be the only DC in the domain, the specs will tell you that. That's the reason for limiting the user accounts to a hard and fast rule of 75 accounts. Anything more than that and you need to go to Enterprise server.

Go to the link and about half-way down you will find your question and if you click on the link, the answer appears:

http://www.microsoft.com/windowsserver2003/sbs/techinfo/overview/generalfaq.mspx

"There can be only one Windows Small Business Server 2003 server in a domain. Each Windows Small Business Server 2003 server is typically connected to the Internet either directly, or via a firewall. Windows Small Business Server 2003 does not support trusts between domains; therefore, user names and resources could not be shared between those Windows Small Business Server 2003 servers. Further, Windows Small Business Server 2003 installs at the root of the Active Directory forest, and it cannot be demoted, or have the flexible single-master operation (FSMO) roles removed."

As far as backup sare concerned, you can save everything so why not backup when the users are at lunch and then again at the end of the day. That way you will be no more than 4 hours out. You can redirect the Documents and Settings folder over to the server and then backup those as you see fit with some sort of replication program.

Message Edited by jmwills on 08-31-2005 03:04 PM

troedel · Answer

Bill,

We have RAID5 with a PERC, three 250GB SATA HDD's, and a fourth 250GB SATA HDD set up as a "hot spare". We are also running a nightly backup of our data. If I understand you correctly, you feel we are protected enough. Is that correct? If so, I will get this information to my principals and try to put their minds at ease. Thank you for your quick response.

Trena

troedel · Answer

jmwillis,

Thank you! That is exactly the proof I was looking for. In regards to backing up at lunch, we only have a half-hour lunch. The server has in excess of 200GB of information. As a result the backup would still be running while people are trying to work. We have tried that before and it doesn't work very well. The backup takes forever and really cuts into the speed of the network. We have no choice other than backing up overnight. Thanks again for your quick response.

Trena

Bill Lally · Answer

Not familiar with SATA drives or their reliability, so no comment on those. I really like SCSI drives, given their past performance and reliability.

Re: do I think you're protected enough - only you can decide that.

However if I came in as a consultant (which I do) and found a well configured Power Edge server completely up-to-date (most recent Dell Drivers installed, hardware warranty in place with same day parts replacement service, Windows 2003 Operating System supported and patched, Anti-Virus strong and current, and nightly backups being made), along with a PERC 4e using RAID 5 AND a Hot Swap drive, I would be comfortable.

That's about the most I will say "on the record" :-)

pcmeiners · Answer

I use SCSI on most of my clients ....   With workgroup servers I used NSI's Doubletake to create a replica server. Regretfully, Active Directory will not allow an exact duplicate server on the network .   If you setup the system with raid 1 with for the OS and a separate raid array for the data you can have a very safe system. You can use the second drive of the raid 1 to create backups, which requires at least one spare drive for the raid 1. The Os setup partition is most difficult to recreate, the data partition, can be restored from tape quite easily. Restore of a raid 1 from image is simple and fast. This is a long read.   http://206.246.253.6/forum/topic.asp?TOPIC_ID=15270   I used to create a single raid 5 array, with two partitions, small one for the OS, second for the data. Even with a hotspare drive I am no longer comfortable with it's safety, as multiple drives can, and do fail in raid 5 arrays. Personally I have been extremely lucky ( I use hotspares),  I have had the hotspares kick in, complete the rebuild, and had another drive fail within hours or on a reboot. This is extremely lucky, most of the time this does not happen, generally the second drive fails during the rebuild of the hotspare.    About raid 6 but read about raid 5 safety limitaions http://www.intel.com/design/storage/papers/308122.htm   For added safety, I would schedule a consistency check of all volumes, weekly from a command line

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Mirroring a server

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