I'm copying a 130 GB SQL Server backup to my Windows 2008 server, and to start with I get write speeds around 80 GB/sec, which is about what I'd expect. However, after the initial burst about a minute into the copy, the disk write speed drops quickly to abround 10 MB/sec.

Any idea what might cause this, or how to fix it?

  • So where are you copying TO and FROM? Is it across a network? What storage sub system are you using? etc. – John Sansom Feb 23 '11 at 22:17
  • I'm copying from a local drive on the same machine. They're just standard internal SATA disks, no RAID etc. – cxfx Feb 24 '11 at 6:36

It is most likely starting off at 80 GB/s initally as the disk cache is used but then as the cache is flushed to disk it will slow down, especially since you are writing to just a single sata disk. The disk writes speed is more then likely an average that is calculated.

Mechanical disks are going to be quite slow and in order to really speed it up you are going to want to look at RAID or SSD.

  • 10 MB/sec seems slow after the initial burst. Is that a typical speed for mechanical HD? – cxfx Apr 16 '11 at 3:26

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