disk access

disk access

[César Soler]

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Hi,

I think I have something wrong in my RH7.2 configuration, because it runs 
very slow (under other OSs it runs faster).
Everything I do seems to be a heavy load for the disks, because the led is on 
all the time (I have 64Mb of memory and a 256Mb swap slice). I would like to 
know what needs such time of disk utilization (which process), something like 
top for CPU or Memory.
could anybody give me any clue?

Thanks in advance,
Best regards.
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César Soler                                      mailto: csoler@euskalnet.net

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Re: disk access

[Mat Harris]

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to find out how fast your disk access is, run 'hdparm -t /dev/<device>'

make sure you only use the -t switch because others will seriously
bugger your disk up.

hear ye, for on the 30 day of the month of August in the year of 2002, César Soler spake thusly:
> Hi,
> 
> I think I have something wrong in my RH7.2 configuration, because it runs 
> very slow (under other OSs it runs faster).
> Everything I do seems to be a heavy load for the disks, because the led is on 
> all the time (I have 64Mb of memory and a 256Mb swap slice). I would like to 
> know what needs such time of disk utilization (which process), something like 
> top for CPU or Memory.
> could anybody give me any clue?
> 
> Thanks in advance,
> Best regards.
> -- 
> -----------------------------------------------------------------------------
> César Soler                                      mailto: csoler@euskalnet.net
> 
> PGP KeyID: 0x179DAD53 at >>>>>>>>>>>>>>>>>>>>>>> http://search.keyserver.net/
> -----------------------------------------------------------------------------
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
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Mat Harris			OpenGPG Public Key ID: CC14DD34
mat.harris@genestate.com	matthewh.genestate.com	

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Re: disk access

[James]

On Fri, Aug 30, 2002 at 06:14:17PM +0200, C?sar Soler wrote:
| 
| I think I have something wrong in my RH7.2 configuration, because it runs 
| very slow (under other OSs it runs faster).
| Everything I do seems to be a heavy load for the disks, because the led is on 
| all the time (I have 64Mb of memory and a 256Mb swap slice). I would like to 
| know what needs such time of disk utilization (which process), something like 
| top for CPU or Memory.
| could anybody give me any clue?

run "top" to see what's using all your CPU and whatnot. The probable
cause is you're running something that needs lots of ram and it's
hitting swap space.

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Re: disk access

[Glynn Clements]

César Soler wrote:

> I think I have something wrong in my RH7.2 configuration, because it runs 
> very slow (under other OSs it runs faster).
> Everything I do seems to be a heavy load for the disks, because the led is on 
> all the time (I have 64Mb of memory and a 256Mb swap slice). I would like to 
> know what needs such time of disk utilization (which process), something like 
> top for CPU or Memory.

For memory utilisation, use "ps axv".

I suspect that a 4:1 ratio for swap:memory may be too high. Swap
should only be used for idle processes. If you don't have enough RAM
to satisfy the active processes, then you need more RAM; simply adding
swap isn't a realistic alternative.

Also, ensure that the disk hasn't been mounted with the "sync" option.

-- 
Glynn Clements <glynn.clements@virgin.net>
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Re: disk access

[César Soler]

El Vie 30 Ago 2002 20:41, wrote:

> For memory utilisation, use "ps axv".

Thanks for the info. I have been looking for something similar, but there are 
too many places to look for... :-)

>
> I suspect that a 4:1 ratio for swap:memory may be too high. Swap
> should only be used for idle processes. If you don't have enough RAM
> to satisfy the active processes, then you need more RAM; simply adding
> swap isn't a realistic alternative.

I left 256Mb for swap slice because I thought to increase the mem amount 
until 128Mb (the 2:1 ratio is the recommend one, isn't it?). I think it's 
time to add it :-)
Anyway, it suprises a simple workstation needs such much memory....... (just 
for simple applications: kmail, konsole, ......).

>
> Also, ensure that the disk hasn't been mounted with the "sync" option.

how could I check it? should this appear as an option in the /etc/fstab file?

Thanks everybody for your answers

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César Soler                                      mailto: csoler@euskalnet.net

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Re: disk access

[Glynn Clements]

César Soler wrote:

> > I suspect that a 4:1 ratio for swap:memory may be too high. Swap
> > should only be used for idle processes. If you don't have enough RAM
> > to satisfy the active processes, then you need more RAM; simply adding
> > swap isn't a realistic alternative.
> 
> I left 256Mb for swap slice because I thought to increase the mem amount 
> until 128Mb (the 2:1 ratio is the recommend one, isn't it?).

2:1 is a very vague "rule of thumb". A better approach is to actually
examine the amount of memory used by processes which are normally
idle.

E.g. on my desktop system I run some common daemons (sendmail, named,
apache etc), as well as the normal system processes (init, mingetty,
etc). These are mostly idle, so I ensure that there is enough swap for
these. Most of the big processes (X, XEmacs, Netscape) tend to be
active, and so need actual RAM.

Currently, I run with 128Mb swap for 256Mb RAM, i.e. 1:2. This is
actually too much swap for this system; I don't think I've ever seen
it use more than about 50Mb of swap.

Basically, if you don't have enough swap, idle processes will consume
RAM when disk space would suffice. If you have too much swap, heavy
memory demand will cause the system to thrash, rather than processes
simply failing.

> I think it's 
> time to add it :-)
> Anyway, it suprises a simple workstation needs such much memory....... (just 
> for simple applications: kmail, konsole, ......).

Right now, I have ~60Mb RAM used[1], and ~6Mb of swap[2]. The largest
processes are the X server, XEmacs and Netscape. No Gnome, no KDE.

[1] That's "-/+ buffers/cache", which is the important figure; spare
RAM is used as disk cache, which will typically result in 99% "used"
once the system has been up for a while/

[2] This is an artificially low figure, reflecting the fact that there
hasn't been any significant contention for RAM since booting, so a lot
of idle processes are still in RAM. Similarly, the RAM figure is
artificially high.

> > Also, ensure that the disk hasn't been mounted with the "sync" option.
> 
> how could I check it? should this appear as an option in the /etc/fstab file?

The fstab file indicates the default options; the mtab file (or the
output from "mount") should indicate the options which are actually in
use (they will be the same unless overridden by explicit arguments to
"mount").

However, I suspect that the problem is more likely to be insufficient
RAM. 64Mb seems to be considered "low end", particularly by some GUI
developers (especially by those who consider "eye candy" to be more
important than conserving memory).

-- 
Glynn Clements <glynn.clements@virgin.net>
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Re: disk access

[urgrue]

>I left 256Mb for swap slice because I thought to increase the mem amount
>until 128Mb (the 2:1 ratio is the recommend one, isn't it?). I think it's
>time to add it :-)
>Anyway, it suprises a simple workstation needs such much memory....... (just
>for simple applications: kmail, konsole, ......).

maybe you should consider switching to a more lightweight windowmanager. 
icewm is pretty nice, and takes very little memory. it should run well in 
64mb of ram, and its not bad at all. (i use it even though i have 384mb of ram)
kde and gnome (maybe especially kde3) are pretty heavy, as are the 
eye-candy windowmanagers like enlightenment.