Archived from groups: comp.sys.ibm.pc.hardware.storage (
More info?)
Dan Irwin wrote:
> Would any of this change in the case of a laptop?
Perhaps. Another metric to consider in the case of a laptop is power
consumption. You might be willing to pay a bit of a premium for
something that won't drain your battery.
>
> CJT <abujlehc@prodigy.net> wrote in message news:<41313203.10705@prodigy.net>...
>
>>Dan Irwin wrote:
>>
>>
>>>Now lets say you had one drive with a 16mb buffer and 12ms avg seek
>>>time and one with 8mb buffer and a 10ms avg seek time. Which would be
>>>better in pratical application?
>>
>>Whichever was cheaper.
>>
>>
>>>CJT <abujlehc@prodigy.net> wrote in message news:<412FF890.2060105@prodigy.net>...
>>>
>>>
>>>>Dan Irwin wrote:
>>>>
>>>>
>>>>
>>>>>So just to confirm a hard drive with a 8mb buffer and a 16mb buffer
>>>>>could conceivably have the documented average seek time, while the
>>>>>16mb one would be faster in real life application
>>>>
>>>>Could be.
>>>>
>>>>
>>>>>CJT <abujlehc@prodigy.net> wrote in message news:<412EF106.9030607@prodigy.net>...
>>>>>
>>>>>
>>>>>
>>>>>>Dan Irwin wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>Where does the ram play into this?
>>>>>>
>>>>>>The computer also has buffers in RAM above and beyond those actually
>>>>>>on the drive.
>>>>>>
>>>>>>
>>>>>>
>>>>>>>Also just so i have it right becacue of the way buffer functions it is
>>>>>>>something that would not affect the seek time on a hard drive
>>>>>>>
>>>>>>
>>>>>>It depends on what you mean. With enough buffers, the computer/drive
>>>>>>combination can also be clever about the order in which pending accesses
>>>>>>are done, which can affect the apparent aggregate seek time (i.e.
>>>>>>avoiding having to seek, or shortening the seeks done, is as good as
>>>>>>brute force speeding up seeks). The devil is in the details. But I
>>>>>>would say the size of the buffers doesn't directly affect seek time.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>CJT <abujlehc@prodigy.net> wrote in message news:<412E28B2.3040208@prodigy.net>...
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>Ruth wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>>it buffers
>>>>>>>>>
>>>>>>>>>ok...enough with the schmarty pants
>>>>>>>>>Buffer is a place to hold data that comes from the drive, that may available
>>>>>>>>>before the CPU is ready for it. If that happens, then when CPU is ready, if
>>>>>>>>>the data isn't available, it has to call the drive up and say "hey you
>>>>>>>>>remember that data i asked for a few nanoseconds ago, well, I need it now"
>>>>>>>>>Without the buffer the drive grumbles and says oh #@#$!! and has to go fetch
>>>>>>>>>it again. With the buffer, the data is stored in some RAM on the drive
>>>>>>>>>electronics so that when the CPU says "OK" ready, the drive says "here you
>>>>>>>>>are right in my hand" and doesn't have to go look again. The advantage is
>>>>>>>>>that its a lot faster to get data from the buffer than from the disk
>>>>>>>>>platters.
>>>>>>>>>It works in a similar way for writing data. If the CPU can dump the data to
>>>>>>>>>the drives buffer to be written when the drive is good and ready, it can say
>>>>>>>>>"good, on to the next thing" instead of having to wait until the disk is
>>>>>>>>>availalbe to perform the the write ....
>>>>>>>>>
>>>>>>>>>Make sense. I hope so. At end of the day, more buffer is better for disk
>>>>>>>>>intensive operations.
>>>>>>>>
>>>>>>>>A couple of embellishments -
>>>>>>>>
>>>>>>>>The drive can be clever about its read buffers, and pre-load into them
>>>>>>>>sectors that haven't yet been identified as desired, but which follow
>>>>>>>>ones that have been, under the assumption that data is often read
>>>>>>>>sequentially.
>>>>>>>>
>>>>>>>>Write buffering has implications for error recovery -- what happens if
>>>>>>>>the power fails (or the machine reboots) while the drive's buffers are
>>>>>>>>full of information that has not yet been written to the disk? As a
>>>>>>>>result, it is often turned off in high reliability systems.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>>"Dan Irwin" <harryguy082589@aol.com> wrote in message
>>>>>>>>>news:2a779348.0408260936.2d99d539@posting.google.com...
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>>I know this is a kind of stubid question, but what does the buffer on hard
>>>>>>>>>
>>>>>>>>>drive do?
>>>>>>>>>
>>>>>>>>>
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