Hi again,
Well, not exactly consensus here. It turned out we'll do it in a whole
different way (see the last solution I inserted):
Four disks will go in a mirrored stripe-set (RAID0+1) and the two other
disks will be defined as hot-spares (what a luxury!) This way we'll have a
logical disk of 18,2GB which is more than enough, because with a
swap-partition of 12,5GB it still leaves me with 5,7GB for root and usr. The
SWXCR-controller will take care of nice i/o-traffic.
Other opinions:
Mervyn Weis (and Annette Lee) wrote:
"I like Option 2. You can use the rest of the disk(s) as Test/Scratch
partitions. I personally like spreading the swap load evenly among the
disks. When swapping becomes heavy, it can only work to your advantage."
While Alan Davis said:
"I would use option one. The difference in sizes doesn't particularly
degrade
performance, and if you were /really/ worried about speed you wouldn't be
using a SWXCR."
Alan Nabeth agreed with this, as he stated that the gain in performance when
configuring equal swap-space sizes is not relevant, because you loose so
much performance when your system starts swapping anyway.
BUT:
Nikola Milutinovic came with a solution I like a lot. And if no-one tells me
that it's is a stupid idea we will implement it this way.
"First of all, these disks we're talking about are behind SWXCR
controller, which means that controller will paralelize access to
physical disks. All you have to do is logically arrange your disks. We'
re always pressed for space, so my favourite configuration is:
5 disks go into RAID-5 = 4 x 9GB = 36GB of "system" (or main) disk
a = (/) 128 MB
b = (swap) 12,5 GB
g = (/usr, /var) the rest (approx. 23 GB
1 disk is a Hot-Spare for this logical drive
So, in case of one disk failure, you're still OK. A disk-shelf failure
would most likely be equivalent of 2 disk failure and you're dead in the
water (the disks could still be OK).
If you go with mirroring, you could go for RAID-1+0 and two Hot-Spare
disks, mirror two, by two, then strip across them."
And that's exactly what we'll go for!
Thanx,
Dagmar
-----Original Message-----
From: Galama, Dagmar
Sent: maandag 7 augustus 2000 17:27
To: 'tru64-unix-managers_at_ornl.gov'
Subject: Equal swap of spare disk?
Hi managers,
Here's a nice configuration-question:
* I have six 9,1GB-disks to install the Unix-environment on.
* Disks are behind a SWXCR-controller
* I need a swap space of 12,5 GB
Now, in my opninion there are two things I can do:
One:
Install Unix on one mirrored disk, using 4GB of swap on its b-partition;
Use one mirrored disk completely for the rest of the swap-space (total swap:
13,1GB);
PRO: this leaves two disks unused, so I can configure them as hot-spare in
the SWXR-controller;
CONTRA: swap is only spread over two disks, and the sizes of the
swap-partitions differ.
Two:
Install unix on one mirrored disk, using 4,3GB of swap on its b-partition;
Use the b-partition of the other disks for 4,3GB swap-partitions (total
swap: 12,9GB);
PRO: swap is spread over three disks, and all partitions are of equal size;
CONTRA: no hot-spares, and disks are not used entirely.
What would you experts suggest? I don't have an insight in the performance
degration when swap-sizes differ, or are spread over two, instead of three
disks.
Any help/suggestion appreciated!
Greetings,
Dagmar Galama
___________________________________________
Dagmar Galama
Origin MS-DS OSS Unix System Management
Building VA-171A P.O. Box 218, 5600 MD Eindhoven
> ( Phone : (+3140-27)89610 FAX : (+3140-27)83962
> * Email : Dagmar.Galama_at_nl.origin-it.com
___________________________________________
Received on Wed Aug 09 2000 - 11:49:04 NZST