Server nearly unusable when doing disk writes
- by Wikser
My question closely relates to my last question here on serverfault.
I was copying about 5GB from a 10 year old desktop computer to the server. The copy was done in Windows Explorer. In this situation I would assume the server to be bored by the dataflow.
But as usual with this server, it really slowed down. At least I could work with the remote session, even there was some serious latency. The copy took its time (20min?). In this time I went to a colleague and he tried to log in in the same server via remote desktop (for some other reason). It took about a minute to get to the login screen, a minute to open the control panel, a minute to open the performance monitor, ... Icons were loading maybe one per second. We saw the following (from memory):
CPU: 2%
Avg. Queue Length: 50
Pages/sec: 115 (?)
There was no other considerable activity on the server. The server seldom serves some ASP.NET pages, which became also very slow in this time.
The relevant configuration is as follows:
Windows 2003
SEAGATE ST3500631NS (7200 rpm, 500 GB)
LSI MegaRAID based RAID 5
4 disks, 1 hot spare
Write Through
No read-ahead
Direct Cache Mode
Harddisk-Cache-Mode: off
Is this normal behaviour for such a configuration?
What measurements could give further clues?
Is it reasonable to reduce the priority of such copy I/O and favour other processes like the remote desktop? How would you do that?
Many thanks!
