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List:       sun-managers
Subject:    Swap space - once and for all
From:       Andrew M Townsend <ATOWNSEND () DOLETA ! GOV>
Date:       1998-02-27 17:41:18
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Hi,

I apologize that this is "non-emergency" but I have been confused about
something for several days now.  I looked around for a more appropriate
list but couldn't find one.  If anyone can point me to one, please do; I don't
have access to newsgroups.

I have searched the Sun managers archive to no avail.  Many closely
related items, but nothing head on.

I am trying to determine _exactly_ how many megs of total swap space I
have, and whether or not it is enough for my system.  I have inherited a
Solaris 2.5.1 box with 128M of RAM.  Here are what I believe to be all the
relevant tables to make the determination:

Part      Tag    Flag     Cylinders        Size            Blocks
  0       root    wm       0 -  336      250.12MB    (337/0/0)   512240

  1       swap    wu     337 -  423       64.57MB    (87/0/0)    132240

  2     backup    wm       0 - 2732        1.98GB    (2733/0/0) 4154160
  3 unassigned    wm       0               0         (0/0/0)          0
  4 unassigned    wm       0               0         (0/0/0)          0
  5 unassigned    wm       0               0         (0/0/0)          0
  6 unassigned    wm     424 - 2732        1.67GB    (2309/0/0) 3509680
  7 unassigned    wm       0               0         (0/0/0)          0

In the format table it states that the swap partition is only ~65 megs,
which alarmed me as 65 megs is hardly 2-3 times our 128MB RAM.  Still
digging, I looked at:

eris# more vfstab
#device         device          mount           FS      fsck    mount   mount
#to mount       to fsck         point           type    pass    at boot options
#
#/dev/dsk/c1d0s2 /dev/rdsk/c1d0s2 /usr          ufs     1       yes     -
fd      -       /dev/fd fd      -       no      -
/proc   -       /proc   proc    -       no      -
/dev/dsk/c0t0d0s1       -       -       swap    -       no      -
/dev/dsk/c0t0d0s0       /dev/rdsk/c0t0d0s0      /       ufs     1       no
-
/dev/dsk/c0t0d0s6       /dev/rdsk/c0t0d0s6      /export ufs     2       yes
-
swap    -       /tmp    tmpfs   -       yes     -

So, the system is using the tmpfs fs type.

swap -l yields:

swapfile             dev  swaplo blocks   free
/dev/dsk/c0t0d0s1   32,1      16 132224  87552

I can't be sure what size blocks those are... 512 or 1024?  The man
pages discuss both.

swap -s yields:

total: 59256k bytes allocated + 49872k reserved = 109128k used, 50784k
available

Is that telling me that there are 59 megs allocated, plus 50 reserved, for a
grand total of 109 megs?  Of which, 50 megs are available?  If that is the
case, then 109 megs is better than the original 65 megs of swap I had
seen in the format table, but it still doesn't come close to the
recommendation of 2-3 times your RAM.  Does that recommendation still
hold true?  The server is primarily a web server with moderate traffic.

Additionally, I ran a vmstat 30 2 and received the following:

 procs     memory            page            disk          faults      cpu
 r b w   swap  free  re  mf pi po fr de sr f0 s0 s6 --   in   sy   cs us sy id
 0 0 0  18008  9168   0   0  0  0  0  0  0  0  0  0  0  113   33   23  0  0 100
 0 0 0  51024  9184   0   0  0  0  0  0  0  0  1  0  0  117   37   30  0  0 100

Which looks promising as it doesn't look like much paging is going on.

Do I have enough space?  Can anyone tell me how many megs of swap I
_do_ have, total, so that I might document it?

Please help.  I know this isn't an emergency but my brain is falling out.

Thanks for your time,

Andy Townsend
Division of ADP Management
Employment and Training Administration
US Department of Labor
(202) 219-5146, x131
atownsend@doleta.gov

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