David Mackintosh wrote: > On Sun, Jun 29, 2008 at 09:08:15AM +0200, Rudi Ahlers wrote: > > Hi all > > > > I want to look at setting up a simple / cheap SAN / NAS server using > > normal PIV motherboard, 2GB (or even more) RAM, Core 2 Duo CPU (probably > > a Intel 6700 / 6750 / 6800) & some SATA HDD's (4 or 6x 320GB - 750GB). > > My budget is limited, so I can't afford a pre-built NAS device. > > My own experience: I have done two NAS systems using CentOS. One is > a HP DL585G1 with four 300GB drives using a hardware RAID-5. The > second is a Dell PowerEdge 2600 with four 300GB drives (software > raid-10) and two 32GB drives (software raid-1). > > One has a multi-core Opteron processor, the other has a high-end > Xeon processor with HT disabled. Both have 2GB of RAM. > > Both are used by high-demand compute processes as NFS servers. > > Despite a lot of fidding, configuring, testing and tuning, neither > result is very good when it comes to NFS performance. We've gone > so far as to run everything as noatime (ie local mount, nfs export, > and nfs client mount) hoping for better performance. > > In comparing the systems we tried the hardware-RAID5 first on the > assumption that HW-Raid5 is faster than SW-Raid, for a higher yield > than Raid-10. However we don't think that the elevator used in the > kernel makes intelligent stepping decisions on the HW-Raid5 because > it doesn't see the "real" geometry of the disks involved, only the > aparrent geometry of the RAID5 disk. > > The Software-Raid10 is better in some ways because the kernel sees > the real disk geometries. Performance is about on par with the > other computer, even though the other computer has the better CPU. > > Due to the hardware involved I couldn't try Solaris 10, but we have > had experiences in the past where the NFS server on Solaris was > significantly better than the NFS server in CentOS/RedHat, both in > terms of throughput and perceved latency under load. > > If I was doing it again, I'd push harder for a budget for a NetApp > filer. For what we are attempting to do, you get what you pay for. > > If I was doing it again with the budget restrictions, I'd probably > try Solaris with software raid. I would then try the *BSD family, > but only after Solaris because I have extensive Solaris experience. On Linux storage servers that use RAID try elevator=deadline for better io scheduling performance. The default 'cfq' scheduler is really designed for single-disk interactive workstation io patterns. -Ross ______________________________________________________________________ This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments thereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and permanently delete the original and any copy or printout thereof.