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From:william drescher Date:July 27 2013 11:31am
Subject:Re: hypothetical question about data storage
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On 7/26/2013 6:58 PM, Chris Knipe wrote:
> The issue that we have identified is caused by seek time - hundreds of
> clients simultaneously searching for a single file.  The only real way
> to explain this is to run 100 concurrent instances of bonnie++ doing
> random read/writes... Your disk utilization and disk latency
> essentially goes through the roof resulting in IO wait and insanely
> high load averages (we've seen it spike to over 150 on a 8-core Xeon -
> at which time the application (at a 40 load average already) stops
> processing requests to prevent the server crashing).

back in the day (many years ago) when I worked for IBM we had 
disk controllers that would queue and sort pending reads so that 
the heads would seek from low tracks across the disk to high 
tracks and then back to low. This resulted in very low seek 
_averages_.
The controller was smart enough to make sure that if a write 
occurred, chronologically later reads got the right data, even if 
it had not been physically written to disk yet.

Is there such a controller available now?

bill

Thread
hypothetical question about data storageChris Knipe25 Jul
  • Re: hypothetical question about data storageVahric Muhtaryan25 Jul
  • Re: hypothetical question about data storageJohan De Meersman26 Jul
    • Re: hypothetical question about data storageChris Knipe26 Jul
      • RE: hypothetical question about data storageRick James26 Jul
        • RE: hypothetical question about data storageJohan De Meersman26 Jul
          • Re: hypothetical question about data storageChris Knipe26 Jul
            • Re: hypothetical question about data storagehsv27 Jul
            • Re: hypothetical question about data storagewilliam drescher27 Jul
              • RE: hypothetical question about data storageRick James29 Jul
                • RE: hypothetical question about data storageJohan De Meersman29 Jul
                  • RE: hypothetical question about data storageRick James29 Jul
                    • Re: hypothetical question about data storageCarsten Pedersen30 Jul
                    • Re: hypothetical question about data storageManuel Arostegui30 Jul
                    • RE: hypothetical question about data storageJohan De Meersman30 Jul