[mythtv-users] Source of my IOBOUND problem?
william_munson at bellsouth.net
Thu Jun 7 11:03:56 UTC 2007
Craig Huff wrote:
> I looked at the man page for iostat some more and saw that the columns for
> rsec/s and wsec/s were for the number of sectors read (or written) per second
> and that sectors are still 512 bytes apiece. The highest numbers I could find
> in the data I collected were under 20K sectors/second each, so worst case
> I am seeing 40K sectors/second of activity with the system maxed out. This
> converts to 20MB/s. My HD is rated at 100MB/s as a PATA drive. No way I
> should be maxed out on throughput at 20% of rated performance. This makes
> me think there's something else amiss.
What does hdparm say your maximum thruput is?
hdparm -tT /dev/hda1
substitute your partition for /dev/hda1. The buffered disk reads is the
number that is most important as that is the actual read speed of your
Here is a sample output from my system
Timing cached reads: 1544 MB in 2.00 seconds = 770.96 MB/sec
Timing buffered disk reads: 168 MB in 3.02 seconds = 55.71 MB/sec
Timing cached reads: 1504 MB in 2.00 seconds = 750.95 MB/sec
Timing buffered disk reads: 216 MB in 3.01 seconds = 71.82 MB/sec
/dev/sda1 is a SATA 300 MB/s drive. As you can see, my motherboard does
not come close to the rated performance and yours may not either. That
tells me that my motherboard is the primary limitation on performance.
Its a 3 year old AthlonXP 3000+ system.
When recording 2 streams from the hdhr plus 2 streams from the pvr-250's
I am maxed out and cannot watch tv. This is with my OS and mysql
activity on a different drive than the storage and both storage drives
in use. I am running SVN using the storage directories feature. If you
are using a LVM your performance will be much worse.
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