| Re: maximum LUN [message #64001 is a reply to message #63928] |
Tue, 25 November 2008 04:10   |
R.Bauer
Messages: 1424
Registered: November 1998
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Senior Member |
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greg.addr@googlemail.com schrieb:
> I made some tests with data reads at different separations to see how
> opening/closing affects the caching. The effect's not large, but
> appears to favour files held open.
>
> Still, if we agree the cost of opening a file is very low, I don't see
> why the number open needs to be rationed so strictly.
>
We don't maintain idl from ittvis. It's leisured to discuss with us why
*they* did something. Add a feature request to their software tracking
page and may be report here what happens (what the developers/product
manager answered).
The idl-pvwave newsgroup is from users for users it is not an official
site from ittvis.
cheers
Reimar
>
> pro filetest
> f1="D:\mydocs\data\hrsc\lev4\2112\h2112_0000.nd4.51" ; ~1 GB each
> f2="D:\mydocs\data\hrsc\lev4\2123\h2123_0000.nd4.50" ;
> a=bytarr(2000,2000)
> for j=0,5 do begin
> distance=(long([0,1e3,5e5,1e6,1e7,1e8]))[j]
>
> s1=systime(/sec)
> for i=0,9 do begin
> openr,3,f1
> point_lun,3,i*distance
> readu,3,a
> close,3
> openr,3,f2
> point_lun,3,i*distance
> readu,3,a
> close,3
> endfor
> s2=systime(/sec)
> print, "repeat open:",s2-s1
>
> s1=systime(/sec)
> openr,1,f1
> openr,2,f2
> for i=0,9 do begin
> point_lun,1,i*distance
> readu,1,a
> point_lun,2,i*distance
> readu,2,a
> endfor
> close,1
> close,2
> s2=systime(/sec)
> print, "single open:",s2-s1
>
> print
> endfor
> end
>
>
> IDL> filetest
> repeat open: 0.12500000
> single open: 0.094000101
>
> repeat open: 0.10899997
> single open: 0.078000069
>
> repeat open: 0.14100003
> single open: 0.12500000
>
> repeat open: 0.14100003
> single open: 0.13999987
>
> repeat open: 0.14100003
> single open: 0.12500000
>
> repeat open: 0.15599990
> single open: 0.12500000
>
> IDL> filetest
> repeat open: 0.13999987
> single open: 0.094000101
>
> repeat open: 0.093999863
> single open: 0.078000069
>
> repeat open: 0.14100003
> single open: 0.13999987
>
> repeat open: 0.14100003
> single open: 0.14000010
>
> repeat open: 0.15700006
> single open: 0.13999987
>
> repeat open: 0.14100003
> single open: 0.14100003
>
> and with the blocks reversed:
>
> IDL> filetest
> single open: 0.10899997
> repeat open: 0.11000013
>
> single open: 0.078000069
> repeat open: 0.092999935
>
> single open: 0.12500000
> repeat open: 0.15700006
>
> single open: 0.12500000
> repeat open: 0.15599990
>
> single open: 0.12500000
> repeat open: 0.15599990
>
> single open: 0.12500000
> repeat open: 0.14100003
>
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