The role of flash in storage

EMC has some SSD/Flash for a segment of their storage systems. The MacBook Air famously has an SSD option. Solid State Disk and Flash are everywhere. So why can't I buy a shelf of it for my server room?

Well, SSD isn't quite ready to go in everything yet. As this blog points out: 1) it is in devices as cache/flash/nvram 2) if the storage isn't engineered properly, there are performance walls to run into 3) availability of dependable SSD is a problem (maybe not for iPods, hahah).

There is one thing I want to try out in the Garden:

http://www.fusionio.com/

Works in linux- Check, ridiculous performance profile for certain activities- Check. I just imagine these with linux RAID, LVM and a database that has a random read profile. I thought about making one as an appliance to shop around. Financing?

NAT in my IPv6? It is more likely than you think...

NAT in my IPv6?

For the good: potentially make it easier to speed up IPv6 adoption.

For the bad: probably break end to end connectivity for some situations.

I hope not. I thought 6 to 4 tunnel was good enough. Guess not.

VMWare appliances to Parallels

Ever found a VMWare appliance or VM that you wanted to run under parallels?

well Virtualization Daily has an answer:

Convert the image from VMWare format to a raw hard disk image using Qemu.

qemu-img convert appliance-harddrive-name.vmdk -O raw appliance-harddrive-name-raw.hdd

There are some caveats: not all VMDKs can be converted, IDE disk only, single disk images (can't have multiple VMDK files). I've had pretty good fortune with Linux appliances so far (because it had the kernel drivers to load up even though the hardware had changed slightly).

They did some sample parallels appliances:

RHCE Self Study

I self studied for the RHCE exam for 5.1 and passed. It was difficult, and I have a solid background in Linux administration.

I used the Michael Jang RHCE self study book, which covers the exam topics. It could really use some sample exercises (like some sample test scenarios). Make sure you get the most recent version. If you can afford it, I think it is generally better to take the 1 week course RH300, after seeing some co-workers and friends take that route.

I would concentrate on reviewing the book then finding weak areas and getting the knowledge of the topics. You need to know everything on the exam blueprint. Then the important thing is working on speed. The main things to remember about the RHCE exam is it is performance based and has a time limit. So you must be able to do the relevant tasks in a quick time frame. Speed is of the essence. If you know one topic really well and can do things quickly, but another at a mediocre level and are slow and constantly referring to apropos or man pages, that may be enough to prevent finishing in a timely manner. Some referral to resources is expected, but you need to know your business and be quick about it.

For me, I was weak at SELinux and ACLs, as I use them very sparingly. So I spent extra time on those above and beyond the self study book and practiced tasks with a hands on manner. Topics that I was strong in, I spent the time reading the book and doing the material, but then I moved on.

The RHCE is a great certification and very satisfying to attain. Redhat's lab performance based exam is a great way to demonstrate linux knowledge. I learned some new things and some new ways to do things as I was studying for the exam.

WRT54G Benchmarks

Alright benchmarked the WRT54G v.3 that I have with dd-wrt v.24. 216Mhz default, no overclock. Basically the thing does everything in software except layer 2 switching and runs out of CPU. I needed to know where the cut off is, because broadband keeps getting faster. You can depend on the box for about 20Mb/s throughput. If you approach that limit, you may run into CPU problems. I also found out the default window size on iperf on Windows client is 8K (too small for 100Mb networks). So all my tests use 256k window sizes (default on linux and os x). All tests were performed with iperf.

Full test notes for posterity:
test 1-LAN bandwidth- both ports plugged into lan ports, same vlan: iperf -s on vista server, iperf -c on OS X client 93.7 Mb/s no CPU on WRT54g.
test 2- LAN bandwidth- both ports plugged into lan ports, same vlan: iperf -s on OS X iperf -c on vista, 61Mb/s (too small a windows size 8K on windows), no CPU.
test 3- LAN bandwidth same as 2, but with real window sizes: iperf -s -w 256k on OS X, iperf -c 192.168.100.8 -w 256k- 93.7Mb/s second switched no CPU.
test 4- routing (no SPI/Firewall) from LAN to WAN same iperf settings as above except client is on the other network - 22.7Mb/s CPU pegged.
test 5- reverse client and server traffic now WAN to LAN- 22.7Mb/s CPU pegged.
test6 - enable SPI/firewall, repeat test 5- 18.3Mb/s. CPU pegged.
test7- reverse client and server now LAN to WAN- 18.3Mb/s CPU pegged.
test8- LAN to wireless- 17.3Mb/s no encryption G only, some 2.4Ghz interference. CPU not pegged, but high (fluctuating between 50-65%).
test9- wireless to LAN- same as above- 17.3Mb/s CPU, not pegged but high (fluctuating between 50-65%).

I should try with WPA, but there is so much interference here. I can't be sure what I'm testing, the wireless, the encryption, the interference.

Summary of results: the switch in the Linksys I have is in hardware- it gives 93.7Mb/s throughput. So L2 performance is good.

Just routing from Lan to WAN with no firewall you can get 22.7Mb/s and it is CPU limited. With a firewall enabled from LAN to WAN, you are limited to 18.3Mb/s and it is CPU limited. Linux iptables style firewall (what dd-wrt uses) is a pretty efficient packet filter (about 10% overhead it looks like).

On the wireless from wireless I got 17.3Mb/s throughput (no encryption), and there was still CPU left. That implies the wireless G protocol or interference will probably be the limit not WRT54G. Basically if you are doing more than 17Mb/s, the WRT54G could be a choke point as could wireless 802.11g. If you want more performance overclock or get a higher CPU dd-wrt capable box and don't use 802.11g wireless. We'll call it 17Mb/s is the upper end for an internet connection for these boxes (due to CPU and 802.11g being limiting factors), more features may make the ceiling a little lower.

GNS3 http://www.gns3.net

So there is a Cisco router simulator called dynamips. I was using it for a while on linux. It is kind of hard to setup and a pain in some ways. Now there is a graphical front end to it:

http://www.gns3.net Graphical Cisco Router Topology emulator

It makes it super easy to lab up simple topologies virtually (no clunky router hardware to dig around with you), and to test configurations and syntax. All you need in gns3 and at least one IOS binary. I used it on OS X, and it worked like a dream. Just get the DMG, click the image, copy GNS to the applications directory, then in the config stage I pointed gns at some images I had on my laptop (my tftp library I keep to upload to the lab). It fired up.

Then you can drag and drop some topologies. Console into the routers, etc.

This site had some nice tutorials for gns3 that the gns3 site doesn't cover.

Another soft skills post

Okay so here are some soft skills tips for IT and general professionalism:

1) Read How to Win Friends and Influence People (there is a nice audio book out there too). A friend of mine called it the Necronomicon he found it so powerful. It really is a good basis if you don't get interacting with people or the beauty of a win-win situation. Non-zero sum games are fun to play.

2) Get a safari account. Even the small one: safari.oreilly.com or safari.ciscopress.com. It allows you to burn through IT reference books that would not be worth having on your shelf after you extract the needed details from them. It is totally worth every penny for an IT professional.

3) If you haven't go talk to some one in another group at your company. Maybe become friends with a couple. It will help you. Sometimes you get advance warning of new projects, sometimes you get a political ally if something unpopular needs to be fought, sometimes you get someone fun to hang out with that has a new point of view. It is all beneficial.