Tuesday, 16 July 2013

Going Live

The State of Things

My four wire case fan arrived last week featuring low speed operation, rubberised frame and unique corrigated design blades. Originally I'd ordered the three wire version by mistake, but this was unsuitable if you want the system board to be able control the fan speed. Then towards the end of the week I worked out how to transfer my databases over for Davical and Mediawiki. I'd already transferred my other mySQL databases by copying the files from /var/lib/mysql, but the Wiki failed to work and Davical uses PostgreSQL. I knew next to nothing about PostgreSQL so it was a slog to work out how the security worked, how data might be transfered, and how to fix the annoying missing PHP library problems along the way. Nothing works without a battle and this was a fresh install, so it should have been easy?! Go-live was now or never, the other apps could wait, and I didn't want to go through the hassle of transferring data again.

On the hardware side, the new fan (an 80mm 'be quiet!' SHADOW WINGS SW1)
required its mounting plugs to be modified, as the plastic locking pins wouldn't go through the threaded mounting bracket. It would have been flimsy anyway, so I discarded the pins, shortened two of the mounting plugs and used a couple of long bolts and washers to secure it. The fan was then plugged into the system fan header on the motherboard and the computer started. It was immediately obvious that the fan was running very slowly, the BIOS reporting just 500 rpm.

Fan mounted using modified only the lower pegs.

Nb, always test things before you modify them, that way if it's DOA you can get it replaced!

That should be just enough to keep a small amount of air moving through the case, and if temperatures heat up, then the fan should speed up to a maximum of 2000 rpm, at a whisper quiet 16.6dB sound level.

Out With The Old

Going live essentially means moving the data and backup disks over to the new server. But before doing this I was keen to compare power usage and disk speeds, (before and after) ultimately reassuring myself that spending all that money was worthwhile.

With all drives running on the old Via C7 based machine the system was shown to draw a steady 32 watts. This dropped to 24 watts after the drives were removed, leaving just the IDE SSD and case fan as additional loads. That's higher than expected for an eleven watt system board, even allowing for power supply inefficiencies.

I used a utility called hdparm to measure the drive speeds. This is a general purpose drive tweaking tool that can perform a multitude of tasks such as optimising speeds and changing time-out parameters. The following command produces two performance measurements:

   pingu:=# hdparm -Tt /dev/sdx (where x is the drive letter to be measured)

DriveCached ReadsBuffered Reads
IDE SSD225Mb/sec28.4Mb/sec
Samsung Momentus HN-M101MBB 2½" sata disk (via IDE to SATA adapter)225Mb/sec29.5Mb/sec
Samsung Momentus ST1000LM024 2½" sata disk (sata port)233Mb/sec30.1Mb/sec
Western Digital Caviar Green 3½" sata disk (sata port)234Mb/sec111.5Mb/sec

It's interesting that the SSD wasn't out-performing the other drives in this test, though in practice it had certainly yielded a performance boost when I'd first installed it. I know they wear out, but I'm sure they don't go slower!

For Shiela.

In With The New

The disks where installed in the new Intel i3 based machine and mount points added to the fstab. These I added using their Block ID rather than their device name, which is a unique drive identifier rather than one that's tied to the port being used. You can find out which disks are connected by typing the following command:

   pingu:=# blkid

The address numbers are a little bit too long to write down and type in manually, so I piped the output of this file into my fstab and edited the result to the correct format.

   pingu:=# blkid >> /etc/fstab

This task completed, I re-tested the disks for speed.

DriveCached ReadsBuffered Reads
Intel 525 60Gb mSATA card6470Mb/sec247Mb/sec
Samsung Momentus HN-M101MBB 2½" sata disk6500Mb/sec103Mb/sec
Samsung Momentus ST1000LM024 2½" sata disk6590Mb/sec100Mb/sec
Western Digital Caviar Green 3½" sata disk (in SATA2 port)6500Mb/sec119.5Mb/sec

There's quite obviously a performance boost but it's surprising that the 3½ inch desktop drive connected to a faster sata2 port wasn't any quicker on buffered reads. To be fair this disk is designed for efficiency and low power with only a 5,400 rpm platter.

Two laptop drives on top and a desktop drive under the mounting plate.

With all disks running the power drawn was just 23 watts, a nine watt saving over the previous machine. That's like turning off a compact fluorescent light bulb that's been burning for the last four years.

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