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4 Posts
1
12715
E20-324 VNX Certification
Hello,
I am struggling with some of the questions in the practice E20-324 tests, I have been uisng the video based course. Can anyone help and explain how to calculate the answer of this example please?
A customer wants to add a SnapView snapshot to a 600 GiB LUN. Captured data show that the LUN has an access rate of 1000 IOPs with a read/write ratio of 4:1, and 8 KiB IOs. What is the expected initial bandwidth at which data chunks will be written into the Reserved LUN Pool?
A. 12.500 MiB/s
B. 1.563 MiB/s
C. 6.250 MiB/s
D. 25.000 MiB/s
Many thanks
andre_rossouw
62 Posts
0
October 9th, 2012 12:00
The SAN Copy transfer granularity is indeed 2 KiB. Bear in mind, though, that this ISC session uses a Clone as the source, and that when a clone is resynchronized, the entire extent will be seen (by ISC) as having changed, and will result in a number of COFWs taking place.
In this example, the 512 GiB source LUN causes the clone to have a granularity of 256 KiB. As the clone is resynchronized, the ISC snapshot sees the full 256 KiB changing, and performs 4 COFWs. Your task is to determine how many of those COFWs will happen in 30 minutes, and to recognize that the full 64 KiB will be copied across the link.
Sissoko1
3 Posts
0
May 17th, 2012 06:00
Hello I am studying for the same exam and I am in the same boat as you. I am looking for a summary formula sheet for many of the questions that require you to know a formula and thus far I have not found anything. If you come across anything please let me know and I will do the same.
Sissoko1
3 Posts
1
May 17th, 2012 08:00
Yes, I have all the PDFs that I could download fromt he pre-requisite training as well as the DVD training and the formulas on how to figure these calculations out are not intuitive to find.
M0nkey_tree
4 Posts
0
May 17th, 2012 08:00
Will do thanks. Are you using DVDs for training?
Sent from my iPad
wwtjoemasi
6 Posts
0
May 17th, 2012 10:00
I just passed the 324 exam this morning and was only given 4 questions that involved the calculations (1 for COFWs, 2 for bandwidth and 1 for IOPs).
The exam has gotten easier in my opinion as I failed with a 50% last month. I agree that the DVDs are not at all a good source for training for this (or any) EMC exam. I just downloaded the PDFs, and read all of the material that was recommended after taking the practice exam.
M0nkey_tree
4 Posts
0
May 18th, 2012 02:00
Thanks, that’s reassuring to hear. I failed last month with 50% too!
SaramiR
7 Posts
3
May 22nd, 2012 03:00
Hello,
The answer will be 12.5MB/s as per my understanding.
When you need to calculate the BW, you must determine the number of 64KB writes.
So in case of random writes, each write is 64KB so the equation will be very simple: BW = # of writes * 64
BW = 200 * 64 = 12800 KB/s = 12.5 MB/s
If sequential, then you have to check size of IO. If IO size < 64KB, then each 64KB will take more than 1 write.
Eg: IO size 8 KB then #of writes per 64KB chunk = 64/8 = 8 therefore, total # of 64 KB writes = # of total writes/8 (in our example # of writes is 200) then: 200/8= 25 then BW = 25 * 64
Sissoko1
3 Posts
0
May 29th, 2012 07:00
Hello:
I managed to pass my exam during EMC World. I believe I had 5 questions that I needed to have some sort of formula to figure it out. I did find the formula from SaramiR very useful. I am not sure if I was able to do some good guess work on the rest of the formula related questions or not, but I got an 88, so I am happy with the results, but I still would like to know the formulas for real work situations when I working with my customers.
Thanks,
Najuma
mforbes1
1 Message
0
May 30th, 2012 19:00
As SaramiR mentioned, and also check out h5773 has the formulas at the end and examples that the vilt left out
http://www.emc.com/collateral/hardware/white-papers/h5773-clariion-best-practices-performance-availability-wp.pdf
M0nkey_tree
4 Posts
0
May 31st, 2012 05:00
Thanks all, appreciate your help.
Regards,
Mark.
vPert
30 Posts
0
July 19th, 2012 03:00
Hi there: I'm currently preparing for this exam and have one more calc which I just don't get:
SAN Copy (ISC) on 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 minutes.
Q: how much is crossing the link during this 30 minutes
I can't find anything value for which the size of the source LUN would matter. ISC has two region sizes 2KB for FLARE > verion 19 and 64KB for FLARE earlier version 19.
any help is really appreciated
Tom
andre_rossouw
62 Posts
1
October 9th, 2012 12:00
That's exactly right.
DinoPierini
1 Message
0
October 28th, 2012 15:00
Does any have an idea, related with this problem:
Your customer has the
following requirements for their CIFS home directories:
- Checkpoint every 10 minutes
- Data retention 24-hours
- Self-service file-level recovery
Which checkpoint interval in minutes should you recommend?
A. 20
B. 30
C. 60
D. 45
I appreciate any comments
Karthik_Kallam
4 Posts
1
April 11th, 2013 13:00
M0nkey_tree
COFW need 3 IOPS (one 64 and two 8/16)
For intial B/W RLP see first IOPS 64
So Initial B/w in this case was No.of write IOPS*64
# write IOPS =1000*0.20(r/w=4:1=>4x+1x=100=>x=.20)
=> 1000*0.20*64=12800/1024=12.5Mib/s
kuroll
2 Posts
0
April 27th, 2013 12:00
i as 2 failed for this exam, actual i have the dvd training but i still failed, so all you have the another document for related for this exam