[EMAIL PROTECTED] wrote:
Adam:
Does anyone have a clue as to where the bottlenecks are going to be with
this:
16x hot swap SATAII hard drives (plus an internal boot drive)
Tyan S2895 (K8WE) motherboard
Dual GigE (integral nVidia ports)
2x Areca 8-port PCIe (8-lane) RAID drivers
2x AMD Opteron 275 CPUs (2.2GHz, dual core)
8 GiB RAM
The supplier is used to shipping Linux servers in this 3U chassis, but
hasn't dealt with Solaris. He originally suggested 2GiB RAM, but I hear
things about ZFS getting RAM hungry after a while.
ZFS is opportunistic when it comes to using free memory for caching.
I'm not sure what exactly you've heard.
"Hungry" clearly had the wrong connotations. With ZFS being so
opportunistic, I had the impression that the more memory thrown at it,
the better, and that it was typically more RAM than an equivalent
Linux/HW RAID box might ask for.
I guess my questions are:
- Does anyone out there have a clue where the potential bottlenecks
might be?
What's your workload? Bart is subscribed to this list, but he has a
famous saying, "One experiment is worth a thousand expert opinions."
Without knowing what you're trying to do with this box, it's going to be
hard to offer any useful advice. However, you'll learn the most by
getting one of these boxes and running your workload. If you have
problems, Solaris has a lot of tools that we can use to diagnose the
problem. Then we can improve the performance and everybody wins.
True, all. I gave some details in the other thread ("ZFS performance
model for sustained, contiguous writes?") from yesterday: My most
performance sensitive requirement would be for one or two streams to
saturate two aggregated GigE links while both reading and writing.
- If I focused on simple streaming IO, would giving the server less RAM
have an impact on performance?
The more RAM you can give your box, the more of it ZFS will use for
caching. If your workload doesn't benefit from caching, then the impact
on performance won't be large. Could you be more specific about what
the filesystem's consumers are doing when they're performing "simple
streaming IO?"
Right, "simple" can be anything to anyone. Let's say writing a 1.5Gbit/s
uncompressed HD Video stream, or streaming out several more traditional
compressed video streams. Other responses in this thread suggest that
pre-fetching will definitely help here, and so ZFS is likely to use that
RAM.
- I had assumed four cores would be better than the two faster (3.0GHz)
single-core processors the vendor originally suggested. Agree?
I suspect that this is correct. ZFS does many steps in its I/O path
asynchronously and they execute in the context of different threads.
Four cores are probably better than two. Of course experimentation
could prove me wrong here, too. :)
Ah, if only I had that luxury.
I understand I'm not going to get terribly far in thought experiment
mode, but I want to be able to spec a box that balances cheap with
utility over time.
Thanks,
adam
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