SUMMARY: Enterprise 6500 configuration

From: Theresa Russo (tar@mc.com)
Date: Tue Jul 21 1998 - 06:06:17 CDT


Thanks to all for your quick response:

        Jeff Wasilko
        David Thorburn-Gundl
        James Ford
        Brian Styles
        Tim Carlson
        Matti Siltanen
        Colin_Melville
        Peter L. Wargo
        Brett Lymn
        
The general consensus to the first question is that there is no added
value and it may introduce problems. I did not provide enough
information on questions two and three.

ORIGINAL POST:

We have just received an Enterprise 6500 server with 2.5GB memory and
three Fibre Channel Clarion Storage Arrays and have been asked to
configure it as follows:

        / and small /usr on internal disk
        full /usr on storage array
        2GB of swap on each storage array

Can anyone help me with the following questions?

        1. What are the benefits of having the /usr partition
mounted from the array?

        2. Is this the right amount of swap space?

        3. Does anyone have a recommended configuration for this
type of system?

--------------------

>
> Can anyone help me with the following questions?
>
> 1. What are the benefits of having the /usr partition mounted from
> the array?

None, and it's likely to cause problems. Depending on what
interface card the Clariion uses (the one from Sun or a 3rd
party), you might not be able to boot from the CDROM to fix a
problem or do an upgrade.

IMHO, the OS should never be on an external array if you can help
it.

----

I could imagine having /usr on the arrays, since one hopes that they are screamingly fast, but I don't see why (except that you mentioned only one internal disk, which means you cannot mirror except on the arrays); /usr is usually not a terribly busy filesystem. Meanwhile, having a small /usr on the internal disk sounds like you want to be able to boot from just the dinternal disk if the array is sicko; this doesn't sound like a really manageable plan to me (but that's just MHO :-) If you plan to load up /usr/local with stuff, then you could certainly put *that* out on the array, but it would, I should think, become a real chore to keep things updated in both copies of /usr (patches are my first thought), especially when one is hiding under the other.

----

How big is the internal disk? I don't actually know if I would mount /usr on the array since it contains system commands. What happens if your array crashes yet all /usr is stored there?

Now, you could have /usr/openwin, /usr/local/, /usr/etc stored on the array. If your array crashed, you couldn't run openwin from the boot drives but you would have access to all files in /usr, /usr/bin, etc.

----

Well, call me old-fashioned, but I'd have / /usr /var and at least some swap on _conventional_ disks. You need only some glitch in the controlling software for your super-whizzbang arrays and you no longer have a machine which will run at all. Apart from other inconveniences, this would make debugging such a problem rather tricky! And, if these arrays are 3rd-party, Sun won't help...

I guess the advantage _ought_ to be speed - transfer rates aren't all that hot from conventional drives. Then again, you'd hardly be transferring Trilobytes/sec from these areas (if you've got enough memory/swap)

----

I don't understand why you would want /usr out on the array.. I think that is a really bad idea. If you ever want to reconfigure the array, you may have to end up moving /usr around..

----

Question - can a sun both off a drive in the clariion fc raid? (we had made a datageneral mini boot off a clariion raid (older scsi version) -> with the system disks mirrored...worked very well :-)

----

1. None, unless you plan on loading lots of junk under /usr (not a good idea, IMHO). The internal disk should be at least 4Gb, probably shipping with 9Gb now. Plenty big for your root, /usr, /var filesystems.

----

Well, the FC disks are faster, but read on for my thoughts We just put in a 64CPU/64G E10000 with 10 A5000's. Generally, if your're using Sun arrays, it's neat to use a disk as boot (works great under 2.6), and another disk on a different array as a boot mirror. In any event, mirroring the boot drive is a *good* idea. What kind of disk-management software are you using?

----

Not much, possibly some speed but that may or may not happen. I can see no reason for just putting /usr on the array. If you are going to put them on the array then put both / and /usr. Having a backup copy of / & /usr on an internal disk is handy just in case the array goes down. Also you may have difficulty installing / & /usr onto the array because the CD image does not probe for LUNs other than 0 so you may not see all the stripes on your array. ----

Terry Russo Mercury Computer Systems email: tar@mc.com Voice: (978) 256-0052 X192



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