Linux on PE2950, PV220S and very slow PV124T

David B. haazeloud at gmail.com
Wed Sep 3 08:49:59 CDT 2008


> Regarding the file count and size, you are not going to make a direct
> backup to tape work, in my opinion.
>
> Each file requires, on average, a disk seek, and each file is only 25
> kbytes.  Your disks can only do 100 seeks per second, and even assuming
> all 8 disks can seek at once that is only 100 * 8 * 25k = 20 MB per
> second.  Your LTO-3 drive cannot operate this slowly.  You can confirm
> this with "iostat -x" when running a backup -- the last column will show
> 100% busy but only a few megabytes/sec throughput.
>   
Hi John,

Here's an iostat, sda1 is VD1 and sdb1 is VD2.
Tape is writing, sda1 is used at 64.93% with very poor throughput.
Seems you're right...
I must try to create a tar on different drive before writing it to tape. 
But restore will be longer, i should restore the entire tar before i can 
extract one file...

Linux 2.6.26 (oi-sauvegarde)    09/03/08

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.80    0.01    1.58   33.82    0.00   63.79

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz 
avgqu-sz   await  svctm  %util
sda              71.38   214.91 190.40 20.21  9413.03  1881.11    
53.63     3.10   14.72   3.08  64.93
sda1             71.38   214.91 190.40 20.21  9413.03  1881.11    
53.63     3.10   14.72   3.08  64.93
sdb               2.11     2.90  8.78  0.25  1076.17    25.27   
122.02     0.06    6.45   1.45   1.31
sdb1              2.11     2.90  8.77  0.25  1076.17    25.27   
122.02     0.06    6.45   1.45   1.31
sdc               3.67    14.07  6.30  2.89  1427.84   135.73   
170.18     0.03    3.77   1.66   1.52
sdc1              0.00     0.00  0.00  0.00     0.00     0.00    
12.52     0.00    2.98   2.67   0.00
sdc2              0.34     8.30  1.31  2.75    71.61    88.38    
39.40     0.01    2.66   1.13   0.46
sdc3              3.33     5.78  4.98  0.14  1356.20    47.35   
273.78     0.02    4.65   2.19   1.12
sdd               3.82     1.57  6.12  0.26  1422.45    14.67   
225.18     0.01    1.75   1.18   0.75
sdd1              0.76     0.35  0.38  0.21     9.13     4.44    
22.90     0.00    3.49   2.17   0.13
sdd2              3.06     1.23  5.74  0.05  1413.29    10.22   
245.92     0.01    1.57   1.11   0.64

Thank you.
David.



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