I’ve been refreshing the hardware for all of my primary systems: desktop, laptop, and dedicated photoshop system. I don’t want to rebuild these systems, so I simply copy the partition(s) off the old systems onto the new systems, and reinstall drivers.
This weekend upgraded my photoshop system. After I copied the partition table, I noticed I was getting a message from linux FDISK to the tune of “partition not aligned on sector boundary”. What the heck is that?
Well, it turns out that new large hard drives (this one is 1TB) have changed their block sizes. Hard drives have had 512 byte blocks for, like, ever. However, between each block is an ‘interrecord gap’ which is dead space. Disk makers want to use that dead space to increase density so they are now making hard drives with 4096 byte blocks. Wikipedia ‘Advance Format’ for the gory details.
All well and fine except only the latest and greatest operating systems can deal with that, so they have built a 512b emulation mode into the drives. However, this emulation mode causes performance degradation. GOOD GRIEF.
So I spent the weekend trying to get my system moved onto the new drive and properly align the partition. I could get the partition aligned, but once I did I could never get the system to boot even though I carefully followed instructions for correcting the boot record and boot sector.
I was fortunately able to get around the problem because I’ve got an older 1TB drive that still has 512b blocks, so I used it as the photoshop system’s boot drive. As soon as I did that, everything moved flawless, just like it should.
Then I looked at my main system and it is misaligned. So I did some performance testing. My main system (XP) and my VM system (64bit Win 7) are both using 10K RPM 1TB velociraptor hard drives. It would be easy to compare aligned with misaligned.
I downloaded and installed HDTUNE on both systems and ran it against their hard drives. The Win7 system that is aligned returned these results:
HD Tune: WDC WD3000HLHX-01JJP Benchmark Transfer Rate Minimum : 106.4 MB/sec Transfer Rate Maximum : 146.6 MB/sec Transfer Rate Average : 130.3 MB/sec Access Time : 6.8 ms Burst Rate : 199.7 MB/sec CPU Usage : -1.0%
the misaligned XP system returned these results:
HD Tune: WDC WD1000DHTZ-04N21 Benchmark - misaligned Transfer Rate Minimum : 42.2 MB/sec Transfer Rate Maximum : 195.4 MB/sec Transfer Rate Average : 149.4 MB/sec Access Time : 7.5 ms Burst Rate : 251.5 MB/sec CPU Usage : 2.9%
Interestingly, over all the misaligned system did a little better though that was probably just chance since this was a one off test on both systems. However, the average transfer rates and the access times are not far off from each other. Well, OK, the aligned drive’s access time is about 10% faster, but the velociraptor’s access time is still nearly twice as fast as a normal drive.
So for the time being, I’m not going to worry too much about whether my partitions are aligned properly. I doubt I’m going to really notice much of a difference. The main difference was upgrading to much faster CPUs and that I definitely see.
I notice the Western Digital has a utility that will align a partition properly, but you have to register to download it (you must own one of their drives), and I couldn’t find any reference as to whether it would deal with straightening out the master boot record and boot sector, so I have not messed with it. If I ever get around to playing with that, I’ll document my adventures.
Jun 29 2014 Edit:
I finally got around to running the WD utility to align the advanced format C: drive in my XP system that has been out of alignment. It seems to have made little difference:
Before After Avg Transfer Rate 144.5 MB/s 153.7 MB/sec Access Time 7.5ms 7.2ms Burst Rate 239.5 MB/s 247.5 MB/sec
Avg Transfer Rate is 6% better, even less than I predicted. Burst Rate is 3% better. Not a very big deal, but the WD utility was pretty easy to run and only took a few hours to align my 500GB of data.
My Seagate drive had no nice utility to convert it, so I had to back it up, rebuild the partition with GPARTED, and put everything back. After I did, the Avg transfer rate was almost identical. Nothing gained on that drive.
So, in my humble opinion, if you can use a utility to align the drive easily, go for it – it helps a bit. If not, don’t worry about it.