[Linux-PowerEdge] Extremely poor performance with LVM vs. RAW disc

Gregory Gulik ggulik at reachmail.com
Thu Nov 1 15:53:08 CDT 2012


You brought up possible bug so I checked the firmware.
Turns out it wasn't current so I upgraded and rebooted.
I'm still testing but it looks WAY faster.  It looks so much better that 
I'm not trusting my testing methodology.



On 11/1/12 2:53 PM, Tim Small wrote:
> On 01/11/12 18:20, Gregory Gulik wrote:
>> the performance of the LVM based filesystem is many times slower than 
>> the raw partition.
>
> Given that writes suffer more than reads, I'm guessing that you 
> probably need to force alignment to the underlying RAID stripe size 
> (and/or possibly the hard disk physical sector size if it is other 
> than 512 bytes) when creating the logical volumes.  i.e. at the moment 
> it seems likely that a single write operation is being changed into 
> two reads and two writes.
>
> BTW if it's a RAID stripe alignment problem, then I believe that the 
> md (linux software) RAID exposes this info to LVM, but the PERC does 
> not make that info available (or lvm doesn't know how to read it).  An 
> enhancement for Dell to carry out perhaps?  That bug must be latent on 
> thousands of Dell systems?
>
> Tim.
> -- 
> South East Open Source Solutions Limited
> Registered in England and Wales with company number 06134732.
> Registered Office: 2 Powell Gardens, Redhill, Surrey, RH1 1TQ
> VAT number: 900 6633 53http://seoss.co.uk/  +44-(0)1273-808309

-- 
Gregory Gulik

email | delivered <https://www.facebook.com/ReachMail> 
<https://twitter.com/Reachmail> 
<http://www.linkedin.com/company/2623532?trk=tyah> 
<http://www.reachmail.net/blog/>
__________________________________________________________________
REACHMAIL Inc.  |  Main 888-947-3224  |  208 S. LaSalle  |  Suite1427 | 
  Chicago, IL 60604
ggulik at reachmail.com <mailto:ggulik at reachmail.com> | Direct 312-229-0132 
| http://www.reachmail.com <http://www.reachmail.com/>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.us.dell.com/pipermail/linux-poweredge/attachments/20121101/5b4802ad/attachment.html 


More information about the Linux-PowerEdge mailing list