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Date:      Tue, 5 Oct 1999 00:23:23 -0400 (EDT)
From:      "Crist J. Clark" <cjc@cc942873-a.ewndsr1.nj.home.com>
To:        bdsq@cc942873-a.ewndsr1.nj.home.com, grog@lemis.com
Subject:   Vinum Used as Swap
Message-ID:  <199910050425.AAA11214@cc942873-a.ewndsr1.nj.home.com>

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I have a general question about vinum... I was not sure to direct it
to freebsd-questions or straight to grog@lemis.com, so I sent it to
both.

I have set up some old SCSI disks as a striped volume. The disks were
not exactly the same size but one was _almost_ exactly twice the size
of the other,

# disklabel da1
[snip]
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  c:  2054864        0    unused        0     0         # (Cyl.    0 - 1003*)
  h:  2054864        0     vinum                        # (Cyl.    0 - 1003*)

# disklabel da2
[snip]
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  c:  4165272        0    unused        0     0         # (Cyl.    0 - 2033*)
  g:  2082636        0     vinum                        # (Cyl.    0 - 1016*)
  h:  2082636  2082636     vinum                        # (Cyl. 1016*- 2033*)

In order to go striped, I had to make all of the subdisks the same
size, which leaves a couple of 10's of MB's unusable on the stripped
plex.

Now, I'm not losing sleep over these extra few MB being idle, but I
have two ideas on how to use them since they are there.

Define the two left over pieces of da2g and da2h as an additional plex
and,

1) Add it as a second concat/striped plex to my big striped volume, or

2) Use it as an extra piece of swap (right now all swap is living on
   IDE drives). If I chose this options is it better to,

   i)  Define a vinum volume with the plex and use it as swap? (Does
       vinum do swap well[0]?

   ii) Should I have thought of this before and cut a da2b partition
       to use the space.

I've read the docs at the website and the manpages and have it up and
working, but I have not developed a real feel for vinum yet. Thanks
to Greg for the contribution to FreeBSD and thanks to anyone with
answers or opinions on how I should or should have set this up.

Oh, and I believe it is customary to include your vinum config file in
a vinum mail (even if the config does seem to be working ;),

drive scsi1 device /dev/da1h
drive scsi2 device /dev/da2g
drive scsi3 device /dev/da2h
volume scsivol
  plex org striped 512k
    sd length 1003m drive scsi1
    sd length 1003m drive scsi2
    sd length 1003m drive scsi3


[0] I only found one off-hand mention about using vinum for swap
anywhere in the docs, vinum(8),

          "setupstate

                               When creating a multi-plex volume,...
                                          ...when using a volume for a file
                               system or a swap partition,..."

I personally believe some mention of the efficacy of vinum as swap, or
lack of it, should be included. That's not to say I might not have
somehow missed it, in which case a pointer would be appreciated.
-- 
Crist J. Clark                           cjclark@home.com



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