how performance of a volume can be reduced by up to 200 percent

Question

i'm not sure if this is the right place to ask

when executing backup of the windows server with Windows backup utility, at the specify destination type screen, there is a note under backup to volume option, this one :

Choose this option if you cannot dedicate an entire disk for backups. Note that the performance of the volume may be reduced by up to 200 percent while it is used to store backups. we recommend that you do not store other server data on the same volume.

i took a screenshot you can find it here

My question is how the performance can be reduced by more than 100 percent ? if the I/O performance measurement is 60MB/s for example, will it be -60MB/s if reduced by 200 percent ?

Answer 1

It is just play of words that say you need longer time to complete particular task, with inappropriate terms.

Say a typical disk will churn out 500 I/O per seconds(IOPS) To store bunch of data that need 2000 I/O to perform, the time required will be

2000 IO / 500 IOPS = 4 seconds (typical task)

Now, say the backup will required 8000 IO, so to complete the backup

8000 IO/ 500 IOPS = 16 seconds (backup task)

When both disk IO task are carry out, now typical task need to compete with the backup task I/O resources, it end up typical task took 8 seconds to return the results.

(8 /4 )seconds = 2 times longer than original task

Apparently smart aleck that proofreading the technical manual attempt to outsmart everyone by replacing 2 times with 200% . While in fact, 2 times is NOT always equal to 200%.