On 6/2/07, Richard Elling <[EMAIL PROTECTED]> wrote:
Chris Csanady wrote:
> On 6/1/07, Frank Cusack <[EMAIL PROTECTED]> wrote:
>> On June 1, 2007 9:44:23 AM -0700 Richard Elling <[EMAIL PROTECTED]>
>> wrote:
>> [...]
>> > Semiconductor memories are accessed in parallel. Spinning disks are
>> > accessed
>> > serially. Let's take a look at a few examples and see what this looks
>> > like...
>> >
>> > Disk iops bw atime MTBF UER
>> > endurance
>> >
>> -------------------------------------------------------------------------
>> > ---------
>> > SanDisk 32 GByte 2.5" SATA 7,450 67 0.11 2,000,000
>> 10^-20 ?
>> > SiliconSystems 8 GByte CF 500 8 2 4,000,000 10^-14
>> > >2,000,000
>> ...
>>
>> these are probably different technologies though? if cf cards aren't
>> generally fast, then the sata device isn't a cf card just with a
>> different form factor. or is the CF interface the limiting factor?
>>
>> also, isn't CF write very slow (relative to read)? if so, you should
>> really show read vs write iops.
>
> Most vendors don't list this, for obvious reasons. SanDisk is honest
> enough to do so though, and the number is spectacularly bad: 15.
For the SanDisk 32 GByte 2.5" SATA, write bandwidth is 47 MBytes/s -- quite
respectable.
I was quoting the random write IOPS number at 4kB. The theoretical
sequential write bandwidth is fine, but I don't think that 15 IOPS can
be considered respectable.
They also list the number at 512kB, and it is still only 16 IOPS.
This is probably an artifact of striping across a large number of
flash chips, each of which has a large page size. It is unknown how
large a transfer is required to actually reach that respectable
sequential write performance, though it probably won't happen often,
if at all.
Chris
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