Re: usb memory stick performance
- From: "M.I.5¾" <no.one@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Thu, 7 Feb 2008 11:54:02 -0000
"Andy Fish" <ajfish@xxxxxxxxxxxxxxxx> wrote in message
news:GEBqj.62945$801.42379@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi,
I am struggling to understand why performance accessing my usb memory
stick is so bad and i wonder if anyone can throw any light on it
my hard disk gives about 40MB/sec for sustained transfers, but when it's
being thrashed (e.g. compiling) it's typically giving 1MB/sec. From this I
infer that during a compile, it's mostly seeking.
my memory stick can give 5-10mb/sec for sustained transfers but with
(presumably) very little seek time. so I thought that by moving the source
files (i.e. the data) onto a memory stick I would get better performance.
however, the performance is substantially worse (2-3x the time taken)
I know it's not the speed of the USB interface because if I use a USB hard
drive, there is a performance increase over having it all on the same
disk.
the only conclusion I can draw from this is that the usb drive has a very
high seek time, which just doesn't make sense
The performance of a FLASH based USB stick will depend on the architecture
of the FLASH chips themselves. There are in fact two supersets of
architecture that have vastly different single reads and sustained reads.
It should also be remembered that FLASH write cycles are comparatively slow,
because even if you change a single bit then the whole block of data has to
be erased and rewritten. Although all sorts of claims are made for read
speeds these generally only apply to a specifically optimised way of reading
the data from the memory core and then only if the reader firmware itself
plays ball. In general terms the speed of a FLASH stick is worse than that
of a hard disc, but having said that some of the very large FLASH chips (8
and 16 Gb) now have write speeds that give hard discs a run for their money.
.
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- From: Andy Fish
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