HP has increased its lead over Dell in sales of servers, according to accounting firm Gartner.

HP's share of first-quarter server shipments grew three percentage points to 30 percent in the first quarter. Dell's share fell to 21.1 percent of the worldwide total from 21.7 percent a year earlier.

Server sales have increased in the last quarter by six percent over the same time last year.  More than 2.1 million units were sold this year.

Shipments of servers using the Unix operating system fell 15.5 percent while revenue from Unix server sales dipped 1.5 percent. IBM came third in the survey.

Sun had the steepest market-share decline, falling from 4.4 percent to 3.7 percent and putting it in fifth place in the Gartner survey.