[mythtv-users] SATA Drive Failure

Allan Stirling Dibblahmythml0015 at pendor.org
Sat Jun 25 12:41:15 UTC 2005

Greg wrote:
>>Ummm... No. You're reading the results wrongly, I'm afraid :) 
>>I would seriously doubt you'd see 1.5Gb / sec outside the datacentre.
>>150Mb / sec... _maybe_.
>>Cached reads are just that - It reads the same sector over and over. 
>>This means it's already in drive's read cache. So what you're 
>>seeing here is the transfer rate from the controller without 
>>(much) SATA latency, no seek latency, no rotational latency. 
>>That's not the test you want. You want 'buffered disk reads'. 
>>This is the (almost real) raw performance of the drive.
>>Here's the results from my array, which is a 8 disk RAID5, 
>>spread over 2 SATA controllers on a PCI-X dual Xeon (yes, I 
>>believe overkill _is_ just a word):
>>hdparm -Tt /dev/sda
>>  Timing cached reads:   2204 MB in  2.00 seconds = 1101.07 MB/sec
>>  Timing buffered disk reads:  374 MB in  3.01 seconds = 124.31 MB/sec
>>The 'buffered disk reads' is the line you're looking for. And 
>>124Mb / sec is quite good for this type of setup.
> Allan, 
> Isnt sda just one of the disks in your array??

No. It's a semi-hardware RAID5

9 disks, 1 as hot-spare.



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