Hi,

We had to migrate the storage of a server on Friday (253 LUNs - 20TB). We decided to create a hot push OR session which we launched with -precopy 3 days before (on Wednesday) expecting that on Friday most of the data had been pre-copied and we had only to copy the final delta minimizing the time the server had to be powered off.

On Wednesday the pre-copy started at an acceptable rate (250 MB/s with pace 5 and ceiling 40%) but on Thursday morning the throughput had decreased down to 1 MB/s or similar values . Many of the LUNs were at 9x% or 100% pre-copied (8 TB out from the 20 TB had been pre-copied) but others LUNs were only at 2%, 3%

My question is why the pre-copy did not continue copying the data at the same rate ?. I can think that maybe as more LUNs are pre-copied the job has to keep track of what changes are done to this LUNs in order to execute the final copy but I'm only guessing.

Do you have any idea of what could be the reason for this ?.

On Friday morning I reconfigured the session and executed a hot pull so we could start the server before the copy had finished.

Thank you

---------------------------------

Sample output of the hot push session:

Session Name          : sarto

           Control Device                         Remote Device             Flags      Status     Done Pace      Name

-------------------------------------- ----------------------------------- ------- -------------- ---- ---- -----------------

                   Protected Modified

SID:symdev         Tracks    Tracks    Identification                   RI CDSHUTZ  CTL <=> REM    (%)

------------------ --------- --------- -------------------------------- -- ------- -------------- ---- ---- -----------------

0XXXXXXXX:3A84    7967660         0 0YYYYYYYYYY:17B5                SD XXXX.S. Precopy           2    1 sarto

0XXXXXXXX:3A80    7926551         0 0YYYYYYYYYY:17B1                SD XXXX.S. Precopy           3    1 sarto

0XXXXXXXX:3A7C    7689385         0 0YYYYYYYYYY:17AD                SD XXXX.S. Precopy           6    1 sarto

0XXXXXXXX:3A78    7433552         0 0YYYYYYYYYY:17A9                SD XXXX.S. Precopy           9    1 sarto

.... [output was cut]

0XXXXXXXX:299C       7684         0 0YYYYYYYYYY:16E9                SD XXXX.S. Precopy          98    1 sarto

0XXXXXXXX:299B          0         0 0YYYYYYYYYY:16E8                SD XXXX.S. Precopy         100    1 sarto

0XXXXXXXX:299A          0         0 0YYYYYYYYYY:16E7                SD XXXX.S. Precopy         100    1 sarto

0XXXXXXXX:2999       3708         0 0YYYYYYYYYY:16E6                SD XXXX.S. Precopy          99    1 sarto

Total              ---------

  Track(s)          198958599

  MB(s)             12434918

Copy rate                      :      1.4 MB/S

Estimated time to completion   : 95 days, 16:24:55