to be clear: you are using high point hardware raid 5 on each controller. so for conroller A - you have 4 250gb drives attached to it, in raid 5 with 1 hot spare = 750gb usable. controller B is the same setup. then, inside of CentOS - controller A raid5 volume shows up as /dev/sda and conroller B raid5 volume shows up as /dev/sdb. then you create a raid 0 stripe of /dev/sda and /dev/sdb which would yield 1.5tb (approx) disk space. then some disks stopped working and you have swapped out the power supply etc. conrtoller A has one disk dead but the hot spare recovered so things are good on controller A (expect for now you don't have a hot spare) and CenOS sees /dev/sda just fine. controller B has multiple disk failures and you only see 1 disk? if this is the case i think your screwed. controller B first has to be able to have enough good disks to build your hardware level raid5 volume, which would then get presented to CentOS as /dev/sdb which is the other half of your CenOS raid-0 stripe. until you can get at least 2 disks running correctly on controller B - your raid-5 volume wont be there. you need 2 of 3 at a minimum, which would be in a recovery state, and slow, but at least running. then, if your CentOS raid-0 won't mount you can start looking at that. is this accurately - recapped? if not, please clarify. TW Woodward wrote: > Hello! > > I need some advice. Here is what happened: > > The set-up: > > Two 4 port High Point 1740 SATA controllers. Each controller had four > 250GB drives attached to it. Each controller was set-up as a separate > RAID5 with one spare drive. In Centos 5 Linux, this created two drives > in /dev, sda and sdb. > > I needed a large storage space, without (as I thought) a high level of > safety. So I partitioned the drives in parted and created sda1 and > sdb1. I then used mdadm to create a RAID0 system across these two > drives. The RAID device is called md0. > > Everything worked fine. It was doing exactly what it was designed for, > which was a large (1TB) temp storage space. Then people saw that it was > a large storage space, so they started storing semi-critical data > (images) there. They stored a lot of this data 300+ GB. Then we had a > power surge. The power surge damaged the power supply. It wasn't > damaged enough to just drop the motherboard or fry a drive, it acted > slowly. It started with one drive on the second controller. It worked > intermittently during one week (while I was on vacation). When I got > back to work on the machine, another drive dropped, then another in > quick succession. > > So I replaced the power supply and hooked the drives back up. Two of > the three dropped drives came back. One of the drives was completely > dead. I was able to add a spare drive and use the High Point supplied > GUI to rebuild the RAID5 array. > > Here is where it stands: sda and sdb appear in /dev. That is good. > sda1 appears in /dev. that is good. sdb1 does not appear in /dev. That > is bad. Apparently, the partition table was dropped on the second > array. When I run mdadm to rebuild, it tells me there is only one drive > (sda1) in the array. When I run parted, it cannot find any partition > information on sdb. > > So here is where I am at. Does anybody know of a way to restore/rebuild > this partition table? Are the tables identical in sda1 and sdb1? What > I mean is, in a RAID0, are the tables written across the drives? Can I > copy the table from sda1 to sdb? How do I do that? > > Thanks in advance. And I already know, it was a stupid set-up, it was a > frail system, etc., etc. But before you let me have it, take this into > account: the power surge was caused by the owner of the company > indiscriminately throwing circuit breakers Even better: he was > throwing circuit breakers with an electrician because they were trying > to determine how to run power down to the new data center. > > TW > > > > _______________________________________________ > TCLUG Mailing List - Minneapolis/St. Paul, Minnesota > tclug-list at mn-linux.org > http://mailman.mn-linux.org/mailman/listinfo/tclug-list >