From: Green, Simon (Simon.Green@EU.ALTRIA.COM)
Date: Thu Jan 15 2004 - 12:03:38 EST
Whilst it's true that migratepv can have a serious impact on I/O, I've used
it during normal working hours on many occasions without anybody
complaining. I've even moved multiple LVs in parallel without problems,
(but I've only done this where the disks were using different hardware:
different adapters, on different I/O busses).
I would say that the most important factor is I/O bandwidth. If there's
sufficient capacity then users probably won't notice anything.
Memory is also important. If the data that the users want is already loaded
into memory then it doesn't really matter what you do on the disks, provided
there's enough CPU capacity to service the I/O requests. If you're doing a
lot of paging, you're more likely to see performance degradation although
even then, if the data is in paging space it doesn't matter what happens to
the actual filesystems. Of course, the data that the users are most likely
to want should be the stuff that's in memory, so in theory it's unlikely
that they'll want to load any pages from the LV you're moving.
It IS dependent on the particular workload as well as the I/O
infrastructure, but although caution is appropriate I wouldn't necessarily
anticipate disastrous results.
For someone unfamiliar with using migratepv, start off with a smallish LV
during a period of low activity and see what happens, then work up.
-- Simon Green Altria ITSC Europe Ltd AIX-L Archive at https://new-lists.princeton.edu/listserv/aix-l.html New to AIX? http://publib-b.boulder.ibm.com/redbooks.nsf/portals/UNIX N.B. Unsolicited email from vendors will not be appreciated. Please post all follow-ups to the list. > -----Original Message----- > From: Frye, Matthew [mailto:Matthew.Frye@REXHEALTH.COM] > Sent: 15 January 2004 16:33 > To: aix-l@Princeton.EDU > Subject: Re: Migratepv Command > > > Oracle doesn't know about it, but you can bet the users will notice. > Migratepv -l has been known to have a noticeable effect on > I/O, especially > with databases. My suggestion would be to coordinate a time > when the system > usage is low(ish). Of course, it depends on the application. > That time may > not exist for your environment.
This archive was generated by hypermail 2.1.7 : Wed Apr 09 2008 - 22:17:30 EDT