realy bad network performance with PowerEdge T610
Michael.Zoet at zoet.de
Mon Feb 21 14:41:36 CST 2011
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Am 21.02.2011 17:21, schrieb Blake Hudson:
> The SAS2008 cards have no cache, while linux softraid will use
> system RAM as a write cache by default. Additionally, most 'desktop
> class' hardware does not honor fsync (commit to disk) requests and
> operates in a forced write-back mode. I'm guessing this difference
> in behavior is causing the high disk activity as well as IO wait you
> are experiencing on the Dell. Applications that issue frequent
> fsyncs (commits) will suffer noticeably because of this.
> The Dell hardware options you have chosen will write data to the
> disks 'safely', while the previous HW configuration probably favored
> speed over data integrity. If you want to go back to speed, you can
> reconfigure the disks as single drives and go back to Linux
> soft-raid. You may also be able to disable fsyncs in your NFS
> exports. Another option is to use a HW RAID controller with battery
> backed cache in write-back mode - like the PERC5/6 or H700/800 cards
> - these would enable fast operation while maintaining data integrity.
> Mount/Export options with 'sync' will honor disk commits and write
> to disk safely; 'async' options will prefer speed, but may result in
> data corruption in the event of system crash/power loss.
Thx for the explanation. Learning by experience... Next time I double
check this. Never thought of buying a system for more than 2.000,- €
to have a RAID controller with NO battery installed. Are the
controller cards H700/800 or Perc5/6 compatible with the H200? I do
not want to reinstall the whole system. Or I have to test my backups.
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