-----Original Message----- From: "Ryan Wagoner" <rswagoner@xxxxxxxxx> Subj: Re: High IO Wait with RAID 1 Date: Fri Mar 13, 2009 12:45 pm Size: 2K To: "Bill Davidsen" <davidsen@xxxxxxx> cc: "Alain Williams" <addw@xxxxxxxxxxxx>; "linux-raid@xxxxxxxxxxxxxxx" <linux-raid@xxxxxxxxxxxxxxx> Yeah I understand the basics to RAID and the effect cache has on performance. It just seems that RAID 1 should offer better write performance than a 3 drive RAID 5 array. However I haven't run the numbers so I could be wrong. It could be just that I expect too much from RAID 1. I'm debating about reloading the box with RAID 10 across 160GB of the 4 drives (160GB and 320GB) and a mirror on the remaining space. In theory this should gain me write performance. Thanks, Ryan On Fri, Mar 13, 2009 at 11:22 AM, Bill Davidsen <davidsen@xxxxxxx> wrote: > Ryan Wagoner wrote: >> >> I'm glad I'm not the only one experiencing the issue. Luckily the >> issues on both my systems aren't as bad. I don't have any errors >> showing in /var/log/messages on either system. I've been trying to >> track down this issue for about a year now. I just recently my the >> connection with RAID 1 and mdadm when copying data on the second >> system. >> >> Unfortunately it looks like the fix is to avoid software RAID 1. I >> prefer software RAID over hardware RAID on my home systems for the >> flexibility it offers, especially since I can easily move the disks >> between systems in the case of hardware failure. >> >> If I can find time to migrate the VMs, which run my web sites and >> email to another machine, I'll reinstall the one system utilizing RAID >> 1 on the LSI controller. It doesn't support RAID 5 so I'm hoping I can >> just pass the remaining disks through. >> FYi - you can potentially get a big performance penalty when running a LSI raid card in jbod mode. The impact varies depending on a lot of things .. Try loading the jbod fimware on the card if it supports this and re run benchmarks david -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
