So it is finally time for a quick write up comparing the various storage options for the iPod.
The test is pretty simple – load up each storage option with the same music, hit play and see how long it takes for the iPod to shutdown. While in actual use the runtimes will be shorter, it still provides a very useful comparison of the different storage mediums.
Test was conducted on the 7.5g iPod Classic, originally came with 160Gb hard drive. I chose this as the original 160Gb hard drive is very efficient as far as spinning platter disks go and the 7.5g itself is the most efficient of this generation of iPods.
Equipment list :-
- 7.5g iPod
- 750mAh Thick Battery (originally 850mAh but it is several years old)
- iFlash Bundle
Storage options :-
- 160Gb HDD OEM (Toshiba MK1634GAL)
- 256Gb SDXC PNY
- 512Gb Dual SDXC (Using 256Gb PNY U1 and 256Gb Kingston SDA10/256Gb)
- 500Gb mSata Samsung 840EVO
- 1Tb mSata Samsung 840EVO
After installation, iTunes was used to restore and sync the iPod using the same 36000 tracks, 220Gb collection – The HDD being smaller than the others only sync’d 150Gb’s worth of music of around 24000 tracks. The 1Tb was synced up with an extra lossless heavy collection to take it up to 45000 tracks 930Gb in size.
Two playlists were created one comprised of 320Kbps MP3 tracks, the other Lossless m4a tracks. I decided to do this as the frequency that the iPod reads from the storage device varies depending on bitrate of the music – e.g. with 320Kbps MP3’s the drive is read every 10 to 12 minutes, where as with a high bitrate lossless m4a the drive is read every 2 to 3 minutes. Very dramatic difference which will have a huge impact on runtime results.
I ran some drive benchmarking tests to get a feel for the read and write speeds of each storage medium. As this was a test from computer to iPod, the results would ultimately be limited to the maximum the USB2.0 bus would allow. Interesting none the less.
The mSata and HDD hit the USB2.0 limits with approx. 22Mb/s read and more importantly for syncing 32Mb/s writes to the iPod. The SDXC/DUAL trails here at approx. 23Mb/s writes and 14Mb/s reads – this is expected as the SD-CF Adapter is spec’d for 25Mb/s transfer rates. The DUAL shows a 1Mb/s improvement on the read speed, this is down to the improved speed of the Kingston card over the PNY.
Lets see what this does for actual iPod use by measuring boot time and how long each storage medium takes to fill the read-ahead buffer in the iPod, this will demonstrate the access times and user experience when scrolling and searching through long track lists.
Interestingly, it looks like the storage read speed does not impact the boot time as much as you would expect. Considering the mSata read speeds are much faster than the SDXC. The SDXC only takes 2 seconds longer to boot – The overriding factor is the time the iPod takes to parse through the iTunes database of 36000 tracks in the case of the SDXC and mSata drive, still the HDD takes close to 50seconds to boot while having only 24000 tracks to parse. As a reference, freshly restored iPod boots up in around 24 seconds.
While the SDXC & DUAL have the slowest raw transfer speeds, they are hands down winners of the Read-ahead and access times test. HDD is the slowest at 7.5 seconds which was to be expected as it takes over 1 second for the drive to spin-up before actually reading any data. The mSata comes in 2nd with a time of 6.7 seconds this maybe surprising but the SATA bus actually takes some time to handshake and negotiate the link from powerup. The SD-CF Adapter is designed to be ready for access in under 100mS, and the SDXC cards have virtually instant access times – which result in a blistering 5.7 & 5.6 seconds buffer fill times.
The User Experience reflects the benchmarking results above – the ultimate in smooth scrolling through thousands of albums, near instant album art display goes to the SDXC and DUAL cards…..
So as mentioned above we have two playlists, one with 320kbps MP3’s (~6Mb per track) and the other with high bitrate lossless m4a files (~30Mb per track).
The iPod was fully charged, reset and booted up, the playlist was selected and played. This was done for the MP3 and Lossless playlist for each storage medium. I setup a low tech IP camera setup to take a photo of the iPod every minute, which allowed me to time exactly when the iPod switched off (to the nearest minute).
This was always the expected outcome, the mSata drives draw quite large currents during powerup and my iFlash-sata itself has a high performance chipset converting a very high speed SATA bus to the slower iPod PATA bus. The HDD returned a solid performance and sits in the middle ground but having the drawback of its limited capacity. The DUAL returned runtime just under 15% less than the single SDXC card.
I think all the devices performed well and will provide most users with plenty of musical enjoyment between charges, and how far are you from a USB charge port in your day-to-day life?
I should point out mSata drives have varying levels of power consumption, several mSata drives in the 240Gb – 256Gb range will return runtimes approaching that of the HDD. In the 500Gb range again there is varying power consumption levels to contend with.
The single SDXC and DUAL returned excellent runtimes, and I think the DUAL requires a special mention – considering in this test you have double the capacity but only a 15% reduction in runtime, the MP3 playlist on a single SDXC running for over 49hours, while the DUAL managing an impressive 43hours.
With mSata, you do trade runtime for the best price per GB, which maybe the choice you have to make if you need the highest capacity while keeping costs down. However the iFlash-DUAL does challenge this idea – 2 x 256Gb SDXC can be bought for less than the price of a single 512Gb mSata!!!
What about CF Cards…..
Well Compact Flash card and the iFlash alone will give you about 25% increase in runtimes compared to the SDXC. But, the price per Gb for the 128Gb plus capacities are just too expensive. I have been fortunate in testing a few high capacity CF card engineering samples and I found compatiblity with the iPod to be suspect, several had badly implemented LBA48 addressing which caused restore loop issues on the 7.5g iPod.
So my advice :-
CF upto 64Gb, SDXC from 64Gb to 256Gb, DUAL from 64Gb to 512Gb+ and mSata from 256Gb and up.
I will update this advice as the solid state storage landscape changes.