Unsolved
This post is more than 5 years old
4 Posts
0
1233
How to find the rate of changed data on a volume
Hi,
I'm working on a replication solutions for DR. I need to know the delta changes on a volume to estimate the bandwidth requirements. As on now, the chekpoints are set at every half-an-hour on the volume.
How to get the delta between two checkpoints?
BR
Murali
gbarretoxx1
366 Posts
0
July 5th, 2010 06:00
Hi,
Please, see the following solution :
https://community.emc.com/docs/DOC-7340
If you simply do a server_df, you will see the difference between the checkpoints :
[root@CS_NS40_1_MSS nasadmin]# server_df server_2 |grep fs01_
fs01_ckpt5 64019696 21496632 42523064 34% /fs01_ckpt5
fs01_ckpt4 64019696 39398480 24621216 62% /fs01_ckpt4
fs01_ckpt3 64019696 37806448 26213248 59% /fs01_ckpt3
fs01_ckpt2 64019696 38800664 25219032 61% /fs01_ckpt2
fs01_ckpt1 64019696 43595360 20424336 68% /fs01_ckpt1
The above output shows the capacity of the production file system (PFS) when each checkpoint was taken or refreshed.
Gustavo Barreto.
Rainer_EMC
8.6K Posts
0
July 5th, 2010 14:00
note that this is the capacity at the time the ckpt was taken and not exactly the change rate
gbarretoxx1
366 Posts
0
July 5th, 2010 16:00
Hi Rainer,
Yes, you are correct.
These values can be used as "estimated change rate" between the checkpoints.
Gustavo Barreto.
mmchalla1
4 Posts
0
July 6th, 2010 00:00
Hi,
thank you for the solution. However, I have seen no changes between the checkpoints generated. Here is the output (I have put that in excel to format and also added date and time for reference)
I have 6 volumes in total accessed by about 500 users 24 x 7, each volume of size 300 GB. Data may be updated as per their requirements. As per the above table - there are no changes at all between the checkpoints?
BR
Murali
gbarretoxx1
366 Posts
0
July 6th, 2010 10:00
Hi,
Let's take these two ones as examples :
When ckpt_data6_ckpt_Schedule_30mins_Past_Hour_033 was created or refreshed, the PFS had 204615608 used.
When ckpt_data6_ckpt_Schedule_30mins_Past_Hour_044 was created or refreshed, the PFS had 205013280 used.
There are changes between the checkpoints.
You can see when they were created or refreshed with :
# nas_fs -i ckpt_data6_ckpt_Schedule_30mins_Past_Hour_033 |grep checkpt_of
# nas_fs -i ckpt_data6_ckpt_Schedule_30mins_Past_Hour_044 |grep checkpt_of
As previously said, this is not the precise change rate, but you can use the difference as a reference.
Gustavo Barreto.
DanJost
190 Posts
1
July 8th, 2010 05:00
A much less-granular but another way to look at the volumes is to check your "level 1" backups - it won't pick up temporary "things" but it will show you what is being added and modified for the day. Depending upon the workload (i.e. it is a file server for end users that don't create tons of temporary/transient files) this might be a good indicator for the total adds/modifies for a day. The checkpoints pick up deletes and while they are "replicated" I don't think they would make you consume a lot of bandwidth. Of course, looking at it this way doesn't show you the highs and lows you may experience throughout the day...
Dan
mmchalla1
4 Posts
0
July 12th, 2010 05:00
Hi,
I have started calculating the difference between the checkpoints and found to be a good base to understand the rate of data change. I thank you all for the help.
Murali