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Go to SolutionHow many COFW when a clone re-sync
We have the following scenario:
Customer requirements call for a SnapView snapshot to be made of a clone prior to resynchronization. The source LUN is 256 GiB, and performs 500 random reads/s and 25 random writes/s of 8 KiB. The clone will be fractured every 15 minutes, and resynchronized after the snapshot is started. How many COFWs will be performed each time the clone is resynchronized?
So I calculated on this but I seem to go wrong some where
this is what I have done:
256GB source LUN so the Extend will be 128GB
Data Marked Dirty = 25 writes x 128KiB extend x 15 minutes x 60 Seconds = 2,880,000
With 8Kib writes it means that you have 64Kib : 8Kib = 8 writes to have a full stripe
So 2,880,000 : 8 = 360,000 COFW
What am I doing wrong ?
Stephanie_P
180 Posts
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Posted October 9th, 2012 07:00
Hi Ron,
The team is going to move this post to the Support Forums Community where your question can be addressed.
Thanks,
Stephanie
There is another one to resolve. I tried the same way which you did and it did not match the answer. Please help,
Sancopy one a clone of a 512GiB source lun, host generates 500 4KiB IOPS with a R/W ratio of 3:1. the clone is fractured every 30 min, How much is crossing the link during this 30 min?
vmauro
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Posted October 19th, 2012 09:00
Hi Ron ...
This is it
Data Marked Dirty = 25 writes x 128KiB extend x 15 minutes x 60 Seconds = 2,880,000 KiB
A COFW deals in 64 KiB chunks, so the data marked dirty must be divided by 64, to give 45,000 COFWs.
Dividing the 64 KiB by 8 KiB, as you did, is only applicable in the case of sequential writes
(From a Senior EMC )