SGI Performance Comparisons

Analysing 6.5 OS Installation Times To Compare CDROM Performance

Last Change: 08/May/2008

This analysis compares the time taken to install the various default IRIX 6.5 CDs for different SGIs with two different CDROM types: 2X and 32X, though the O2 tests use an internal 12X to compare to the 32X.

The focus is on two areas: how much better a faster CDROM is compared to a slower CDROM for a particular system, and how much better a given CDROM can be utilised given the presence of a better CPU.

Refer again to tables 1 and 2:

                               ******* Sub-Task Completion Times *******
                               (16%) (51%)  (86%)  (91%)  (94%)   (100%)
                   CD   Read   Pre-                       Inst    End of  End of
                   ROM  Inst   inst  F 1    Apps   F 2    Tools    Exit   rqsall
                        Tools  Ends  Ends   Ends   Ends   Ends     Coms   ELF libs

O2 R5000SC/200:    32   0:42   0:54  06:31  15:07  16:46  17:45   22:52   0:34:06
O2 R5000SC/200:    12   0:46   0:54  06:58  16:04  18:05  19:20   24:08   0:35:28
I2 R4400SC/250:    32   0:47   1:11  06:45  15:17  16:57  17:55   23:12   0:36:05
I2 R4400SC/250:     2   1:16   1:11  09:18  21:06  23:28  24:38   29:57   0:42:31
Indy R4400SC/200:  32   0:42   1:26  08:32  19:42  21:40  22:50   29:41   0:45:24
Indy R4400SC/200:   2   1:16   1:26  11:11  25:49  28:29  29:58   36:53   0:52:35
Indy R4600PC/133:  32   0:44   1:45  11:48  28:26  31:28  33:07   46:11   1:08:45
Indy R4600PC/133:   2   1:16   1:45  14:10  33:37  37:12  39:00   52:05   1:14:39
Indy R4600PC/100:  32   0:35   2:04  12:36  30:18  33:36  35:20   48:28   1:12:11
Indy R4600PC/100:   2   1:16   2:04  15:01  35:33  39:32  41:28   54:54   1:18:36

         Table 1: Detailed Timings for a Default IRIX 6.5 OS Installation


                   CD   PRE-                       INST-  EXIT   RQSALL
                   ROM  INST   F1    APPS    F2    TOOLS  COMS    ELF

O2 R5000SC/200:    32   0:54  05:37  08:36  01:39  00:59  05:07  11:14
O2 R5000SC/200:    12   0:54  06:04  09:06  02:01  01:15  04:48  11:20
I2 R4400SC/250:    32   1:11  05:34  08:32  01:40  00:58  05:17  12:53
I2 R4400SC/250:     2   1:11  08:07  11:48  02:22  01:10  05:19  12:34
Indy R4400SC/200:  32   1:26  07:06  11:10  01:58  01:10  06:51  15:43
Indy R4400SC/200:   2   1:26  09:45  14:38  02:40  01:29  06:55  15:42
Indy R4600PC/133:  32   1:45  10:03  16:38  03:02  01:39  13:04  22:34
Indy R4600PC/133:   2   1:45  12:25  19:27  03:35  01:48  13:05  22:34
Indy R4600PC/100:  32   2:04  10:32  17:42  03:18  01:44  13:08  23:43
Indy R4600PC/100:   2   2:04  12:57  20:32  03:59  01:56  13:26  23:42

   Table 2: Individual times for each installation step (IRIX 6.5)

This time, we're interested in the stages which do involve the CDROM, namely: reading the installation tools, installing F1, APPS, F2, and INST TOOLS.

Table 11 shows how much faster a 32X CDROM is compared to a 2X CDROM (12X for O2) for each installation step that uses the CDROM. The figures are obtained by dividing the faster time by the slower time for each system (ie. 100*(1-x) is the percentage improvement, where x is a number from the table).

                                        INST- 
                    F1    APPS    F2    TOOLS     AVERAGE

O2 R5000SC/200:    0.93   0.96   0.82   0.79   |   0.91
I2 R4400SC/250:    0.69   0.72   0.70   0.83   |   0.71
Indy R4400SC/200:  0.73   0.76   0.74   0.77   |   0.75
Indy R4600PC/133:  0.81   0.86   0.85   0.92   |   0.84
Indy R4600PC/100:  0.81   0.86   0.83   0.90   |   0.84

Table 11: Speedup using 32X vs. 2X CDROM (vs. 12X for O2)

(remember the above table only includes the installation steps which use the CDROM)

Obviously, the better the CPU, the bigger the speedup when switching to a faster CDROM. For low-end Indys, it really isn't worth upgrading to a very fast CDROM because the main CPU can't exploit it (don't be fooled by the 0.84 figure; remember that half the installation time is taken up by tasks that do not use the CDROM - these tasks do not change when using a faster CDROM, so the benefit of having a better CDROM is averaged out).

The O2 results compare a 32X to a 12X; the main conclusion to be drawn is that using a faster CDROM than the O2's internal 12X isn't really worth it, but it would be worth it if one has an older O2 system with a 4X internal CDROM.

As further evidence, Table 12 shows how much faster each system is compared to the Indy R4600PC/100 when using a 32X CDROM.

                                        INST-
                    F1    APPS    F2    TOOLS     AVERAGE

O2 R5000SC/200:    0.53   0.49   0.50   0.57   |   0.51
I2 R4400SC/250:    0.53   0.48   0.51   0.56   |   0.50
Indy R4400SC/200:  0.67   0.63   0.60   0.67   |   0.64
Indy R4600PC/133:  0.95   0.94   0.92   0.95   |   0.94
Indy R4600PC/100:  1.00   1.00   1.00   1.00   |   1.00

Table 12: Performance compared to Indy R4600PC/100
          when using a 32X CDROM.

Quite clearly, better processors can exploit faster CDROMs to a greater degree. Note especially the almost insignificant change when comparing R4600PC/133 to R4600PC/100. Now compare Table 12 to Table 13 below which shows the same calculations when using a 2X CDROM (O2 results excluded).

                                        INST-
                    F1    APPS    F2    TOOLS     AVERAGE

I2 R4400SC/250:    0.63   0.58   0.59   0.60   |   0.60
Indy R4400SC/200:  0.75   0.71   0.67   0.77   |   0.73
Indy R4600PC/133:  0.96   0.95   0.90   0.93   |   0.94
Indy R4600PC/100:  1.00   1.00   1.00   1.00   |   1.00

      Table 13: Performance compared to Indy R4600PC/100
      for each installation stage when using a 2X CDROM.

Notice that the figures are higher than those in Table 12 as one might expect (ie. slower), with the exception of Indy R4600PC/133; ie. low-end systems are bottlenecked by their limited CPU power, not the theoretical performance of the CDROM.

Table 14 shows the proportion of time spent using and not using the CDROM. Clearly, whatever the combination of CDROM and CPU, roughly half the overall installation time does not involve using the CDROM. The last column (FACTOR) shows how much faster each installatin was compared to the slowest installation (R4600PC/100 with 2X CDROM).

                         TASKS    NOT
                   CD    USING   USING    TOTAL   CDROM   
                   ROM   CDROM   CDROM    TIME    USAGE  (FACTOR)

O2 R5000SC/200:    32    16:51   17:15   0:34:06   49%     0.43
O2 R5000SC/200:    12    18:26   17:02   0:35:28   52%     0.45
I2 R4400SC/250:    32    16:44   19:21   0:36:05   46%     0.46
I2 R4400SC/250:     2    23:27   19:04   0:42:31   55%     0.54
Indy R4400SC/200:  32    21:24   24:00   0:45:24   47%     0.58
Indy R4400SC/200:   2    28:32   24:03   0:52:35   54%     0.67
Indy R4600PC/133:  32    31:22   37:23   1:08:45   46%     0.88
Indy R4600PC/133:   2    37:15   37:24   1:14:39   50%     0.95
Indy R4600PC/100:  32    33:16   38:55   1:12:11   46%     0.92
Indy R4600PC/100:   2    39:24   39:12   1:18:36   50%     1.00

                 Table 14: Task Summary for CDROM usage.

In order to come to a conclusion as to whether a CPU upgrade or a CDROM upgrade is a better choice, one must compare the total time taken for the installation when using a slow vs. fast CDROM (this is not the same as Table 11 which only covered the stages which used the CDROM). The results for this are in table 15.

                   OVERALL
                   SPEEDUP

O2 R5000SC/200:     0.96
I2 R4400SC/250:     0.85
Indy R4400SC/200:   0.86
Indy R4600PC/133:   0.92
Indy R4600PC/100:   0.92

Table 15: Overall speedup using
32X vs. 2X CDROM (vs. 12X for O2)

The results are clear: if one has a low-end CPU, upgrading to a fast CDROM does not improve software installation speed because the main CPU isn't good enough to take advantage of it; plus, the portion of the installation which doesn't use the CDROM is going to be pretty slow anyway. Only when one moves to CPUs which have reasonable clock speeds and L2 cache does one see any real benefit from using a fast CDROM.

One can also glean from Table 15 that it isn't worth using a faster CDROM when installing software on an O2 which has a 12X internal CDROM, but it would be worth it if the O2 was an older model with a 4X CDROM. In case you've never tried, external CDROMs are handled just fine - one is given a list to choose from on the software installation menu, and IRIX shows numerically labelled icons on the GUI desktop (CDROM1, CDROM2, etc.)

This has been a detailed analysis, but it's not the whole story. What about other types of operation which use a CDROM? What about copying files straight to disk? See the next section for further CDROM tests.