[OS X TeX] TeX Performance (MacMini)
Peter_Dyballa at Web.DE
Mon Feb 7 08:25:09 EST 2005
Am 07.02.2005 um 12:51 schrieb Steffen Wolfrum:
> Hm, does it really make sense to have a fast external drive for the
> MacMini - regarding its Firewire 400(!) ?
It's theoretically 400 MB/sec -- no rotating disk can reach this
transfer speed! They (2,5") usually have an internal limitation to
40...50 MB/sec. The usually used ATA interfaces have in (very old) PIO
modes less than 20 MB/sec, in Ultra DMA mode 100 MB/sec transfer rate.
So you can connect via FireWire or USB-2 a bunch of fast disks fr
parallel access ...
> Wouldn't it be much more efficient to have this 7200RPM Hitachi
> Travelstar 7k60 inside the Mini? Or is this drive really that loud (as
> it was written sometimes) that I would spoil my silent Mini with this?
The number of revolutions per minute is not the only important factor.
Imagine a platter of 20 GB at 7.200 and one with 30 GB at 5.400. The
difference in data is 50%, the difference in speed is only 25%, or, in
other words: with the same number of cylinders (data tracks) the slower
disks shows 50% more data to the read/write head!
The 7K60 has a density of up to 50 Gbit/in², my Fujitsu MHT2080AT has
70 Gbit/in² leading to 40 GB per platter or 20 GB per side -- so it can
rotate slower. The coming Fujitsu MHU2100AT will have 25 GB per side,
more than 80 Gbit/in². And they have 8 MB cache, being able to sustain
a high data rate some more msec ...
I have to admit that both (slow) Fujitsu disks have a longer
track-to-track and latency time -- they don't mean a thing to you since
you'll never use files or applications that span more than one cylinder
of a few 10 MB! One read -- all data's in memory, one write -- all
output saved. For a fat DB or fat swap files because of not enough RAM
the Hitachi might be a better choice -- or an external RAID of 3,5"
disks at 10,000 RPM. Somewhere away in the not to close neighbourhood
Check from time to time c't: they're testing disks. I can check for you
and send you a remark or result in spring (that's when the MHU2100AT
will come, 150 €, maybe more -- or less).
Mit friedvollen Grüßen
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny..."
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