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Saturday's SILUG meeting

Steve and I had a lot of elbow room at Saturday's meeting. Tai and Emma
joined us, of course.

Steve shared a work story that shows the downside of massively parallel
interconnects in a rack. One bad cable will cause bizarre behavior and
challenge your troubleshooting abilities.

We spent quite a bit of time discussing the relative merits of using zfs
or ext4 software RAID filesystems on my pod. I'd elected not to go with
zfs because the pod's PC motherboard could not support deduplication.
Indeed, no motherboard on earth could support the 1T of RAM needed to
support dedup for the pod's full 140T capacity. My current task is to
use a second set of five 4T drives to build a LVM array, copy everything
from the first array (/dev/md0), then use its drives to grow the LVM

Steve pointed out this would be a lot easier to do with zfs. Aside from
its inability to support dedup on the pod, I was a bit nervous about
using zfs because of an ongoing incompatibility between EPEL's dkms
package and the zfs-dkms package from the Spacewalk repo. Steve
explained the source of problem and assured me the patches that resulted
in the Spacewalk fork were being applied upstream to the dkms package.
The conflict should be resolved soon.

Steve also described how using block transfers between two zfs
filesystems could be faster than file transfers between zfs and ext4.
That's a real consideration when terabytes are involved. Long story
short, I'm now zeroizing all five drives in the new /dev/md1 array and
have written the zfs pool creation script. It took 18.5 hours to zeroize
nine 300G drives on a system with 8 cores. The pod has 4 cores, so five
4T drives may take several days to zeroize at a 10.xx load factor.

On another subject, I noted that the now Belkin-owned Linksys has
announced a successor to their legendary Linux-based WRT54G router. The
new WRT1900ac will support 802.11ac speeds, have four gigabit Ethernet
ports, four antennas, a 1.2GHz dual-core processor, and full support
from OpenWRT, DD-WRT, and tomato when it is released this spring. $299.
I want!

Finally, if anyone knows a NetApp-qualified storage admin with a TS/SCI
clearance looking for a job, have them contact me.

Next scheduled meetings: First Wednesday February 5 from 6:30-8:30pm,
and third Saturday February February 15 4:00-6:00pm.


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