Hello Group,
We are looking at possibly reducing our memory usage and making our SLES9
z/Linux "better". There are different opinions about what to do and
what the costs are.
A). VM Memory Disk (VDISK). Currently we do not use VDISK for our production
zLinux servers on our z/VM 5.2 system. I see SLES 10 recommends two
VDISKs. Is there a downside to using VDISK? About the only thing I saw is
that VDISK doesn't do expansion or contraction, so you may need to
"monitor" its usage. The popular thing I can see is to VDISK the swap
filesystem, which we don't do. It sounds to me that even if you only have one
zLinux you want to use VDISK (at least for swap).
B). Shared Kernel. This is an NSS and not just a DCSS for the filesystems like
"/var" (I think "/" or root is not supported in a DCSS anymore). So
this is what I IPL. If it's not there, I can't IPL. We have been kicking this
idea around for a while. But with only a dozen penguins of different
configurations (WebShere or not, monitors etc.), I'm not sure we would gain
much. Again I looked at what it costs. I found this in the IBM
literature: "Every virtual machine that IPLs your shared system must have the
same disk configuration as the system that was saved. That is, the
disks must be at the same addresses and be the same sizes as the virtual
machine that issued the SAVESYS command". What this means to me is we need
every zLinux that IPLs the NSS has to have the same filesystems (in size and
number). Furthermore I found that previously it looks like LKCD (Suse
Crash Dump) didn't work well when you IPLd an NSS. All I can find now is that
there appears to be a new LKCD2. I also found LKDTT, but it requires a
kernel patch and a kernel re-compile. I thought re-compile = unsupported
(tainted) zLinux? So then who would want your dump? Do we need to
re-compile the kernel for "crash dump" support? Does it matter if we IPLd from
an NSS? Are there any kernel parameters related to using an NSS? I
saw a post from this year that talks about "Boot from NSS support" and a
parameter "SAVESYS=". If we go through with this for only a few penguins is
this worth it (besides having a good procedure to grow the farm)?
Thank you, Dave H.
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