How fast are SD cards compared to a standard hard drive?

[Dylan_94_2]

I was thinking about getting crafty and having windows or ubuntu installed onto an sd card that i can boot from on my EEE pc, using the two internal ssd's for storage only. But my i don't want to do it if it would be painfully slow. How fast are SD cards compared to a standard HDD

[Shogoll]

Being solid state I believe they're slightly faster, but most SD drives are connected to the rest of the computer through a pretty shitty bandwidth limited connection like a USB Bus or something, which limits the speed of the SD dramatically, usually to below shit-HDD levels.

[Tezza1234]

SD is slow, The maxiomum class of SD is 6MB/s, Much much less than most 7200RPM HDDs

[Dylan_94_2]

Damn. Currently i have ubuntu on a 1gb micro sd and plugged into my eee pc via an adapter, and it doesn't seem all to slow, but its hard to tell. Seeing as i couldn't install ubuntu onto my micro sd card, i have to run it like a boot disk.

[birkett]

Read speed, great. Write speed, shit.
Random read, shit.

[yngndrw]

Very slow sequentially, quite a bit quicker for small / random accesses.

I believe they have limited erase / write cycles.

[pebkac]

SD cards have way slower (less than 30MB/s unless maybe some extreme versions) read/write speeds than most harddrives (can be faster than 100MB/s). SSD drives are faster than normal HDs only because they have multiple flash chips reading/writing in parallel, while sd cards and thumb drives have only 1 chip in them .