From: Albretch M. <lb...@ho...> - 2006-12-14 00:34:03
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After reading smartmontool's FAQ and a number of other tutorials/info, I still don't quite understand why is it that smartmontool is not or can not be used in a -software- RAID conf. I also wonder why not so many people do this . if you do a search on 'smartmontools "software raid"', you will see many people reporting "weird beaviors" and all kinds of other unwanted/unexpected etceteras. . There is a question in smartmontool's FAQ, "Can I monitor disks behind RAID controllers?", that address -RAID controllers-. However, since smartmontool works on a hardware level and -software- RAID works on an OS level basically, I don't see why smartmontool is not used in -software- RAID confs? . Also, could you point me to good links and possibly books on all things hard drives including their physicall guts, tools to deal with them, ...? . Something I notice is that some hard drives are placed vertically in some computers and horizontally in some others, but I think (actually it could be even proved) drives (their mechanical parts) are a lot less taxed if they spin vertically, but I don't hear of anyone talking about these kinds of things ... . thanks lbrtchx _________________________________________________________________ View Athletes Collections with Live Search http://sportmaps.live.com/index.html?source=hmemailtaglinenov06&FORM=MGAC01 |
From: Volker K. <lis...@pa...> - 2006-12-15 07:13:44
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> After reading smartmontool's FAQ and a number of other tutorials/info, I > still don't quite understand why is it that smartmontool is not or can not > be used in a -software- RAID conf. I also wonder why not so many people do > this Actually I'm always doing that. Software raid is using the kernel's md devices. You can access each disk individually behind the md device as much as you please. Ergo, zero trouble for smartmontools. In the case of a raid1, the kernel has to write data to both disks (= twice the PCI bus load). As a bonus, you can raid only parts of disks in any way you please; partitions don't have to be at identical disk locations but should still have equal size. Hardware raid on the other hand gives you a well-endowed controller card which has firmware on the card to handle all the disks, the raid functions, and the array management. To the computer, this card presents as a single hard disk. The kernel can access this new disk, but the card's physical layout does not allow access to individual disks for the kernel. Dead end for smartmontools, unless the card's firmware kindly forwards smart-specific commands between the kernel and the disks. Most cards don't, and I understand all which do need special support for this data shuffling in smartmontools. The there's a type of IDE controller which calls itself raid controller. Don't you get sucked in. It's just an IDE controller card with a bit of BIOS extension on it to create an array and make itself look like a raid card. Often they come with a proprietory driver, which does nothing else than the Linux md driver does anyway. It still uses the mobo CPU for the raid computations. Promise rubbish features prominently in this category. Treat these cards as an IDE card and turn all raid functions off, that's its only use. Likewise, any mobo raid stuff is in this category too. Useful as additional IDE channels only. Oh yes, no trouble here either for smartmontools, since it's exactly the same as, say, the primary and secondary cable on your mobo. Volker -- Volker Kuhlmann is list0570 with the domain in header http://volker.dnsalias.net/ Please do not CC list postings to me. |