Software Mirror a Database

[Mad_1]

I am using D-Class servers (HP-UX 10.20) currently, data store in Sybase with RAID 5 (Model 20).

The server will be upgrade to A or L class, my HP sales recommend to use sc10 as data storage with software mirror (MirrorUX). They said the CPU can perform mirroring efficiently.

Since sc10 can be hot swapped, if one of the mirrored disk is down, the database service should not be interrupted, the replaced disk can be synchronized.

But my concern is, is it need to stop the database during data synchronization, or need to restart the database after data synchronization?

Please help, thanks

[Justo Exposito]

Hi Ryan,

If you have mirrorUx software, the sinconization process impact in the througput, but you don't need to stop your database. This is a O.S process.

Regards,

Justo.

[Vincent Farrugia]

Hello,

You can continue to run normally while a syncronisation is made. Of course, you will have a performance drop during this time, though.

HTH,
Vince

[Wim Rombauts]

Mirroring is fine and you can continue to work when a disk fails, but remember, when you use mirroring, you will need almost double as much disks as you should need in a RAID5 configuration.

Mirroring offers a higher degree of protection (multiple disks can go down, in RAID5 only one can go down and then you are unprotected). You can configure a hot spare to automatically take over the defective disk. But you will need more disks and there *IS* a CPU overhead. If a mirroring configuration with a "cheaper" disk box is less expensive than a configuration with a hardware RAID5 disk box, I think mirroring is a good choice.

[harry d brown jr]

Ryan,

If you want better performance for your data, I suggest adding an fc60 in front of the sc10, and I actually suggest an fc10 over an sc10. If you are going to an L then get fibre channel cards.

live free or die
harry

[Mad_1]

Thanks a lot for all your reply.


All I worry about is one of my colleague mentioned that in AIX, a database (raw device) need to restart after a software mirrored disk is replaced and need data synchronization. I afraid it will also happen in HP-UX.

It is my first time to post message here, I found it is very helpful, thanks all again.

[Justo Exposito]

Hi Again,

This is because your collegue is using a raw device and then the device is not under the O.S. In your case if you have the database files under the HP/UX file system and with mirror/ux you don't have this problem.

Best Regards,

Justo.

PD: It's your first time, then don't forget to put your points to the replays.

[Darrell Allen]

Hi Ryan,

Yes, once you replace a disk the logical volume mirrors for that disk will need to be re-synchronized. However, there are commands that allow you to do this with the system up and running. Technical Knowledge Base document# KBAN00000347 gives instructions. I've attached it for your convenience.

My memory about AIX is fuzzy but I'm fairly certain you can mirror or re-sync logical volumes in AIX without stopping the app using those LVs.

Darrell

[Mad_1]

Actually, I am using raw device too in HP-UX, the Sybase database is storing in a raw device, so I am worry about "Does software mirroring can handle this - not interrupt a Sybase database (raw device)?"

As far as I understand, the MirrorUX (software mirroring) mirror the data in system level, all it knows is VG or LV, it doesn't care about whether it is a raw device or a file system, therefore, it sync the data block by block when one of the mirrored disk was replaced. Is it correct?

[Roger Baptiste · Accepted solution]

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Yes, you are correct. As long as you have the mirroring setup correctly for all the VGs on the system, it should work fine . When a disk fails, the database will still run since it has two copies (primary and mirror disk).
When a new mirror disk is attached, it will get synchronised automatically in the background. You don't need to bring the database down. But, during the synchronisation, there will be some performance bottlneck.

HTH
raj