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BC resynchronization time

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Madej
Advisor

BC resynchronization time

Hi

I have to create BC for database which has 70 TB.
Storage is a XP12000.
When BC will in PSUS/SSUS state a large amount of changes will occur on primary volumes - about 12 hours in split state.
How many time will resync go on? From what it depends except changes?

Thanks for reply

Madej
5 REPLIES
Amar_Joshi
Honored Contributor
Solution

Re: BC resynchronization time

Madej,

It's more part of a BC design rather than estimating the sync time. To maximize the throughput between PVOL and SVOL and to minimize the SYNC time there are several factors, should be considered when designing the BC:

1. PVOL and SVOL should come from different Array Groups. (most important)

2. Best possible, PVOL and SVOL Array Groups should be connected on separate ACPs (DKA).

3. Best possible, PVOL and SVOL Array Groups should not be sharing LDEVs with other hosts.

4. RAID level will play a major part too, 7D+1P will outbid 3D+1P speed and so as 14D+2P will outbid 7D+1P. Faster disks such as 15k RPM, will be better performing than the 10k RPM.

On top of it, when running the SYNC several other factors will be considered for the performance:

1. How busy the XP is?

2. How much cache installed (BC operation creates side-files in cache).

3. Several small volumes will perform better than that of bigger volumes. e.g. 280 x 250GB volumes will sync faster than the 35 x 2TB volumes. (You don't have control over it but good to know).

4. Host operations on the PVOLs should be avoided while the SYNC is going on, that will improve the read performance from the PVOLs.

5. On top of all, the SYNC depends on how much data was "changed" on PVOLs during the SUSPEND period.


Hope all these will help you explaining the SYNC period.
Madej
Advisor

Re: BC resynchronization time

Thanks a lot.
It very helps.

But I thought that PVOL and SVOL disk group have better SYNC performance when connected to one ACP. But I have small experience.

I have to plan BC for DB which will only one on XP12k, even on two XP12k. A problem is the DB is growing - 1TB per week ;-)

Regards
Madej
Madej
Advisor

Re: BC resynchronization time

I have two questions else:
How is the max read and write speed on one disk group in RAID5 7D+1P?
and
How is 1 pair ACP throughput?

Thanks for any help

regards
Madej
Amar_Joshi
Honored Contributor

Re: BC resynchronization time

Madej,

Attaching the XP performance whitepaper, look at the pages 8 - 12 for XP12000 performance characteristics for different RAID configurations.

This is a life saving book for most of the architects.

Enjoy !!!
Aashique
Honored Contributor

Re: BC resynchronization time

Hi,
My database size is currently now 450GB. I used pairsync every night 12.For your huge size of database you can pairsync 4times.

Thanks & Regards
Aashique