03-05-2008 05:10 AM
Is there any overhed when accessing files from an vxfs snapshot (compared to accessing from the "original" filesystem).
We have some strange performance problems showing a very high "wio" when running a dbcheck from a snapshot.
(rx2660, HP-UX 11.23, application is "clearcase")
03-05-2008 05:48 AM
If the dbcheck involves writes to the snapshot filesystem the situation is expected.
clearcase is something I work with on Linux and HP-UX and it can be quite troublesome and at times I/O intensive.
Owner of ISN Corporation
03-05-2008 12:29 PM
Thank you for your reply.
Do you run any dbcheck on the clearcase database ?
On snapshot filesystem ?
Have you checked the load on the system when dbcheck is running (using e.g. sar or glance) ?
In our case, most of the time dbcheck is running, "usr" and "sys" activity is only a few %, rest is "wio". Somtimes, almost all the load is "wio". At that time, some copy operations seems to happen.
cp -Rp /backup/wds_swt.vbs/db /tempo/db_checklog/db_copy
(/backup is a snapshot filesystem)
Know very little about clercase myself. I have only been asked to have a look at the performance issue of the server.
03-05-2008 04:21 PM