A place for Unix Thoughts and Ideas

Monthly Archives: July 2012

Mapping OS Devices to Veritas Device names in Veritas 5.1

With Veritas 5.1, if you are using native DMP, enclosure based naming is mandatory.

Now this is good as 5.1 has enhancements where the device name now includes the LDEV number for the array and it makes it easy for storage grows.

But this can kind of be a PITA if you are building fresh or you don’t have the LDEV number and are just trying to find the veritas device name for a set of luns.

This is a expansion of a 1 liner I posted awhile back, it has been expanded to include the Veritas Device name in the output.

Here it is and you can copy/paste it into a bash session. You can change the order and padding by modifying the awk statement

for c in $(iostat -En | grep Soft | awk '{print $1}' | cut -d t -f1 | sort | uniq); do 
for i in `iostat -En | grep Soft | awk '{print $1}' | grep "$c"`;do 
vxdisk list $i &>/dev/null || continue
DEV=`vxdisk list $i | grep Device | awk '{print $2}'`
SZ=$(iostat -En $i | grep Size | cut -d'<' -f2)
echo "$i ${SZ%% *} $DEV" | awk '{printf ( "%s\t%s %4d GB (%d MB)\n", $1, $3, $2/1024/1024/1024+.05, $2/1024/1024+.05) }'
done | sort -t d +1 -n; done

This is the output of vxdisk list

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Strickly Limiting ZFS arc cache size

On the majority of my servers I use ZFS just for the root filesystem and allowing the arc to grow uncheck is counterproductive for tracking server utilization and running some applications.

Consequently I severely limit the amount of memory used and set it at 100MB.

If your going to limit the arc cache, just about every ZFS tuning guide suggests capping the arc cache limit via zfs:zfs_arc_max

However, I was digging into the memory utilization of one of my Tibco servers and noticed that the ZFS arc cache was quite a bit larger than value specified in /etc/system

root@testserver # kstat zfs:0:arcstats:size | grep size | awk '{printf "%2dMB\n",  $2/1024/1024+0.5}'

I actually noticed this before in the past, but didn’t research any further due since it was insignificant compared to the free ram on that server.

I checked a couple other servers and noticed that it was consistently around 2GB for most of my servers.

root@testserver # grep zfs /etc/system
set zfs:zfs_arc_max = 104857600

In checking Kstat, I noticed a minimum parameter for zfs that I hadn’t noticed before that looked very similar to my arc size.

root@testserver # kstat -p zfs:0:arcstats | head -4
zfs:0:arcstats:c        2101237248
zfs:0:arcstats:class    misc
zfs:0:arcstats:c_max    104857600
zfs:0:arcstats:c_min    2101237248

Referring the Oracle Solaris Tunable guide, the zfs_arc_min parameter is set to 1/32nd of the physical memory or a minimum of 64MB. 2GB on a 64GB system, 4GB on 128GB one.

So I now include the maximum and minimum values in /etc/system and now the limits are occurring as predicted.

root@testserver # grep zfs_arc /etc/system
set zfs:zfs_arc_max = 104857600
set zfs:zfs_arc_min = 104857600

root@testserver # kstat -p zfs:0:arcstats | head -3
zfs:0:arcstats:c        104857600
zfs:0:arcstats:c_max    104857600
zfs:0:arcstats:c_min    104857600

root@testserver # kstat zfs:0:arcstats:size | grep size | awk '{printf "%2dMB\n",  $2/1024/1024+0.5}'

Now that I have realized that the majority of my servers have arc caches set to 1/32 of ram, I can take a good look at whether I should increase my intended defaults or leave them as is.

Vertically mounting the new Airport Express

Apple recently released a new update to their Apple Express product.

I have been very pleased with my Airport Extreme. However, now that I finally got a iPad and have been using it various spots around the house, I have been noticing a definite drop off on the wireless reception on the back half of my house.

This is easily solved with  “extending” my current “ wireless network.

Now I like all the improvements on the new airport express, primarily the ability to extend the network on both the 2.4 Ghz & 5Ghz  bands, but I’m one of those people who really liked how nicely the old one just hung off a outlet on the wall.

Looking at the plug for the power cord and I realized it look very familiar and fit perfectly with the my left over power plug from my macbook pro.

Now I can happily let sit on the wall.

Now I will admit that this is probably not the most optimum placement for the antenna. But for how I’m using it, it is perfect!