MobileRead Forums - View Single Post - Speed of on-board storage vs. MicroSD

davidfor · 01-15-2018, 01:41 AM

If you are talking sideloaded book, then probably not.

The problem is the covers. For sideloaded books, the device generates covers from the books as needed. That means when you scroll through the book list for the first time, it is generating covers as you go. The cover are cached in memory, so going back and forth over a few pages should be reasonable fast.

But, if the books are on the main storage, the generated cover images are stored on the main memory for reuse later. That means, if the cover images have been generated and have dropped out of the cache, the images are read from the disc and not regenerated from the book. That should be a lot faster.

For sideloaded books on the SD card, the cover images are not saved. This means that they are regenerated each time they are needed and aren't in the cache. So, paging through a list of books on the SD card will probably be slower than for the main memory.

If you are using calibre, you can alleviate this. The device will use any cover images it finds on the SD card. The driver can generate and send the cover images for both the main memory and SD card. If you already have the books on the device, my Kobo Utilities plugin can generate and send the covers to the device.

Note: All that ignores the possibility that the SD card is faster than the main memory. Or that splitting the IO between the main memory and SD card should help the performance.

01-15-2018, 01:41 AM	#2
davidfor Grand Sorcerer Posts: 24,905 Karma: 47303824 Join Date: Jul 2011 Location: Sydney, Australia Device: Kobo:Touch,Glo, AuraH2O, GloHD,AuraONE, ClaraHD, Libra H2O; tolinoepos	If you are talking sideloaded book, then probably not. The problem is the covers. For sideloaded books, the device generates covers from the books as needed. That means when you scroll through the book list for the first time, it is generating covers as you go. The cover are cached in memory, so going back and forth over a few pages should be reasonable fast. But, if the books are on the main storage, the generated cover images are stored on the main memory for reuse later. That means, if the cover images have been generated and have dropped out of the cache, the images are read from the disc and not regenerated from the book. That should be a lot faster. For sideloaded books on the SD card, the cover images are not saved. This means that they are regenerated each time they are needed and aren't in the cache. So, paging through a list of books on the SD card will probably be slower than for the main memory. If you are using calibre, you can alleviate this. The device will use any cover images it finds on the SD card. The driver can generate and send the cover images for both the main memory and SD card. If you already have the books on the device, my Kobo Utilities plugin can generate and send the covers to the device. Note: All that ignores the possibility that the SD card is faster than the main memory. Or that splitting the IO between the main memory and SD card should help the performance.