Diomidis Spinellis wrote:
quoted text
> Diomidis Spinellis wrote in freebsd-stable@:
>> I can't get an Ultrium-2 LTO drive to stream, and (I think) I've 
>> traced the problem to the read performance of the USB2-attached NTFS 
[...]
quoted text
>> I'd appreciate any suggestions you may have.
> 
> Today I upgraded the machine to  8.0-CURRENT, and obtained similar results:
> -  5372041 bytes/sec reading an NTFS file
> - 15369758 bytes/sec reading from the raw device
> 
> The raw/FS read performance difference with UFS is a lot lower:
> - 33162654 bytes/sec reading a UFS file
> - 47221133 bytes/sec reading from the raw device
> 
> I'd welcome any ideas on why the NTFS layer makes reading three time 
> slower than reading from the raw device and suggestions for improving 
> the performance.  I'd also be happy to work on improving the situation, 
> if I get any pointers on where to start.

[Apologies for talking to myself.]

It looks like the problem is the small (4K) block size NTFS uses for its 
requests.

iostat -t da -zx -w 1
NTFS file:
device     r/s   w/s    kr/s    kw/s wait svc_t  %b
da0      1329.6   0.0  5318.5     0.0    1   0.7  95


Raw device:
device     r/s   w/s    kr/s    kw/s wait svc_t  %b
da0      234.8   0.0 15024.4     0.0    1   6.3 100

iostat -z -w1
NTFS file:
       tty             ad0              da0               cpu
  tin tout  KB/t tps  MB/s   KB/t tps  MB/s    us ni sy in id
    0   77  0.00   0  0.00   4.00 1324  5.17     0  0  1  0 99
    0   78  0.00   0  0.00   4.00 1331  5.20     0  0  1  0 99
    0   78  0.00   0  0.00   4.00 1322  5.16     0  0  0  0 100
    0   79  0.00   0  0.00   4.00 1331  5.20     0  0  0  0 100

Raw device:
       tty             ad0              da0               cpu
  tin tout  KB/t tps  MB/s   KB/t tps  MB/s    us ni sy in id
    0  228  8.00   1  0.01  64.00 236 14.73     0  0  0  0 100
    0   78  0.00   0  0.00  64.00 235 14.67     0  0  0  0 100
    0   78  0.00   0  0.00  64.00 235 14.67     0  0  0  0 100
    0   78  0.00   0  0.00  64.00 235 14.67     0  0  0  0 100


Diomidis Spinellis - http://www.spinellis.gr

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