Using mirror-ux vs hardware level mirroring

[Debbie Beresford]

We are currently on an RP5470 system running HP-UX 11.0. Mirroring is done with an I20 - 4si - raid card. We are upgrading to HP-UX 11.23 and have found this raid card is not supported.

We are currently looking at 2 options:

1. Replace the raid card with another type of raid card
2. Use Mirror-UX and mirror at the software level.

Does anyone have any suggestions? Have you found there is a performance hit using software vs hardware mirroring? System performance is not currently a problem for us. Also, we are running Oracle databases if that makes a difference.

I look forward to hearing of any experiences/advice you may have.

[Steven E. Protter · Accepted solution]

Shalom Debbie,

I think the industry agrees that doing it with hardware is better. Mirror/ux is the best raid software I've ever used, but hardware raid lowers the strain on the system CPU and leaves it for other work.

See Charles Keenan, HP-UX CSE

SEP

[Carlos Roberto Schimidt]

Hi,

Hardware mirroring is better, but if you want mirror just your filesystem from vg00, my sugestion is to use mirror-ux.

I dont have perfomance trouble using mirror-ux just for mirror operation system.

But if you want mirror Database for example, my sugestion is for use hardware mirroring.

Schimidt

[Jeff Schussele]

Hi Carlos,

In my experience I've found that Mirror-UX imposes a very small penalty due to having to complete two writes...BUT...you can actually gain read performance because the kernel will place the read request on the smallest queue.
And neither is worth a darn if they're using the same controller path. *Both* HW and SW mirroring should *alway* have separate paths to whatever disk device(s) is(are) being used.

My 2 cents,
Jeff

[Jeff Schussele]

I should have also added that we hardly ever use mirror+stripe or stripe+mirror on our RAID arrays. We *always* use RAID 5 - it just as robust, faster & a *hell* of a lot cheaper.

Rgds,
Jeff

[Debbie Beresford]

Thanks everyone for your input. I will forward this on. Does anyone have any suggestions for controller cards?

[Patrice Le Guyader]

hi Debbie,

As all have said, hardware raid is better but mirror UX is a good software. If it can help, we have hundreds of servers, HPUX and SUN. All of them have mirrors for systems disks made with software and there's no problem. And even on High end servers like Superdome or SF25K.
For one application, we've made a mirror between two arrays and this is done with mirrorUX, the only small problem is a high activity of vxfsd daemon, but it's running well for many hundred giga of data.

Hope this help.

Regards
Pat.

[Debbie Beresford]

Thanks for your help everyone.

[Debbie Beresford]

Looks like we'll go with hardware mirroring. Thanks for your help