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mirroring

mirroring

Can i get eveyones opinion on mirroring sybase, i have sybase ver 12.0 running on hpux ver 11.0 with 2 16g harddrives mirrored thru lvm, but sybase has a mirror option also, so i am wondering if anyone has used both and which they liked or if anyone has any opinions as to which one is better to use.
thnxs for you help
michael
Just another HPUX Admin
7 REPLIES
Jeff Schussele
Honored Contributor

Re: mirroring

Hi Michael,

As a rule HW mirroring is better than SW mirroring. But in this case both are SW mirroring.
So I'd prefer the mirroring be done as close to the OS as possible - in your case LVM would be my choice. For the simple reason that the kernel can keep tabs on LVM.
You'd have to show me hard, realistic data to convince me that a vendor's mirroring scheme would perform better with the same/better level of integrity that I know I can get w/LVM.

My 2 cents,
Jeff
PERSEVERANCE -- Remember, whatever does not kill you only makes you stronger!
Fragon
Trusted Contributor

Re: mirroring

Hi,Michael:
My situation is just the same as you. But my DB is PROGRESS. I use MirrorDisk/UX.
I also think the O/S SW mirror is better because the system itself integrate with it. I am not sure whether Sybase's mirror can have a good performance!

-Live as you wish-
Gerald Zhou
Trond Haugen
Honored Contributor

Re: mirroring

Looking at this from a OS point of view I would Mirror the vg00 volumes (be sure to make both disk bootable and test it). and already haveing done that I would use LVM for the database volumes too. In addition thare are the reasosns mentioned by Jeff & Gerald.

Regards,
Trond
Pierce Byrne_1
Frequent Advisor

Re: mirroring

Mirror at the OS level. Two of the advantages are 1 - Its easier if you ever migrate from sysbase to another RDBMS as the mirroring is in place. 2 - Moving to a disk array with hardware RAID is simple, no database config changes required.
Not knowing too much about sysbase I cannot comment about efficiency etc. but HP will have tuned LVM mirroring for HP hardware can you be sure that Sybase have done the same?
Steve Post
Trusted Contributor

Re: mirroring

I have mirroring of sybase at the hardware level, not LVM, and not sybase. It's EMC software. I don't think I would run both sybase and LVM mirroring on at the same time.
Martin Johnson
Honored Contributor

Re: mirroring

We did both. We found maintenance was less/easier with Mirror/UX as our databases grew and we moved things around.

Eventually, we went to hardware mirroring with EMC drives.

HTH
Marty
Jeff Schussele
Honored Contributor

Re: mirroring

Hi Michael/Marty,

I've actually had to do both HW & SW mirroring on a VG PV before.
Had an existing mirrored VG that resided on a Jamaica that needed to grow & there was no more space nor PVs available anywhere for this system except for it's EMC.
User did not want ANY downtime so I was forced to extend the VG out to the EMC where it happily gobbled up 8GB of actual diskspace to get the 4Gb of LUNs that LVM was going to *strictly* enforce on it to get the 2Gb of volume extension.

Bet if we'd been charging the cust for actual diskspace occupied back then they would have given me the outage to do it right. :~)

Cheers,
Jeff
PERSEVERANCE -- Remember, whatever does not kill you only makes you stronger!