Hard Drive bandwidth

I got at least 75 MB/s with my 2008 MacBook and a 160 GB HDD (5.400 RPM). Maybe your HDD is failing?

 

Try doing "cd /" then "grep -r a * > largefile.txt". If there isn't much stuff for it to list, it won't reach its peak speed.

 

Hrm. I got 122 on my 2006 CD MacBook. It has a 7200 HDD. If I'm looking at the right place.

 

Your crude benchmark will not take disk fragmentation or file size into account (likely explains why your own macbook is so slow) - many large files = faster than many small files.

However, in terms of IOs per second (which generally is a more useful measure than megabytes per second) under random IO, for reference:

7200 rpm data = ~70-80 per second (this is as fast as the heads can re-position for random reads)
SSD = 4000-8000+ per second (no head repositioning time).


If you're streaming large, non-fragmented files a hard drive will perhaps get 100-120 meg per second (vs say 200-300 for an SSD). If you're doing random 4k reads, that may drop to 300k per second (75-80 IO operations x 4k per sec).

An SSD will stay fast (up around 200 meg per second) doing random IO.


THAT is why an SSD kills for performance in most day to day things - multi-tasking disk access is not totally random, but its not very sequential. Even if your SSD only did 80 meg per second, it will still be faster than a spinning disk for most day to day use, because most day to day use (other than file copies) doesn't involve sequential streaming. Even a "slow" SSD will be far more responsive.


Even if your IO controller on your macbook is a bottleneck, your access patterns will likely be faster with SSD - because peak throughput is not what you're typically doing.



edit:
the raptor on USB getting 40 meg peak is about all you can hope for (USB bus saturated). hook it up to firewire and you'll likely hit 80 meg / sec (firewire saturated). a raptor on anything other than thunderbolt (or SATA) will be bottlenecked by the bus.

Your macbook should have a SATA2 bus in it, which can do 3gigabit. So, up to 300 meg per second, in theory... you aren't currently bottlenecked by the bus.