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Technology Stocks : WDC/Sandisk Corporation -- Ignore unavailable to you. Want to Upgrade?

To: Pam who wrote (32513)	6/14/2006 9:42:20 AM
From: SBHX	Read Replies (2) \| Respond to of 60323

When you need to open a file, a lot of complex datastructure operations come in to play. For example directories and file structures follow a file table like structure on the storage itself. Sometimes, these data structures get cached in memory by the OS to accelerate access so that only the actual payload (file data themselves) can be read. When reading sequentially, high performance 10000RPM SATA HDD are clocked over 80MB/s, normal 7200RPM sata ones will be closer to 60MB/s. Assuming the reported 20MB/s sequential rd/wr numbers of the SSD flash are correct, that makes the SSD flash 1/3 to 1/4 the speed of the HDD. However, the HDD is a mechanical device, and before data can be read, the head(s) have to be positioned to the correct track/cylinder (seek time) and you have to wait for the appropriate sector (rotational delay). Random seek times for fast drives are 5ms and closer to 12ms in normal drives. Compared to solid state devices like flash, (Guessing here) I doubt random seek time is anywhere close to 10ms, so when when you take that into account, with normal workoads, I suspect the flash will still come out overall faster.