How do you define large? Yes, for guests greater than 4gb, you can
measure "bad things" when reorder occurs. For 30GB guests, really bad
things occur. But reorder prior to 6.3 is important, or you have to buy
a lot more real storage and real storage is expensive. The storage
algorithm in 6.3 is something I like, BUT the paging in 6.3 is going to
have some interesting challenges that seem designed to sell solid state
paging devices.
So turn reorder off for large guests or you will have "spiky response
times", the larger the guest, the longer the spikes.
On 1/15/2014 12:29 PM, Veencamp, Jonathon D. wrote:
I don't mean to hijack Ted's thread on the swap differences he's seeing between
SLES 11 SP2 and SP3. I have a different issue, and his issue is more immediate.
I'll make a different thread on my issues. I'd like to get some feedback on VM
SET REORDER OFF for large hosts...
Jon
-----Original Message-----
From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Barton
Robinson
Sent: Wednesday, January 15, 2014 2:23 PM
To: LINUX-390@VM.MARIST.EDU
Subject: Re: Swap behavior change between SLES 11SP2 and 11SP3?
With all of the installations (100s) i've worked with using vdisk for
swap, this would be the first complaint i've heard with the exception of
some bad configuration defaults. If you had really good performance
management tools, I'd be happy to look at the data.
On 1/15/2014 5:44 AM, Veencamp, Jonathon D. wrote:
Ted,
I can't speak to the differences between kernels, but also I am very interested
in your thread. Our SLES10 and SLES 11 experience has been that even with
VDISK as swap on a VM system that is NOT overcommitted on memory, that any
linux swapping is just kills us with the same sort of results you describe in
your 1GB vs. 3GB test. Which is a shame, ZVM VDISK should give us more
flexibility than it seems to.
So I will hope someone else chimes in with some VM wisdom I don't know.
Jon Veencamp
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