Re: To partition or not to partition MD arrays (Was Re: smartctl cannotaccess my storage, need syntax help)
On 19/01/24 at 20:14, Nicolas George wrote: Franco Martelli (12024-01-19): One case against using partitions on mdraid: if your array gets messed up, you get to recreate those partition tables yourself and that's just hilarious if you don't have a backup. Happened to a friend of mine, reason was a UPS brownout. How can I get a backup of mdadm RAID partition? You do not need a backup of the RAID partitions, that would be terribly inefficient. You need a backup of the partition table. Yes, I agree of course. I was asking this to Anssi because it looks like strange to me to have the backup of the partitions, as he pointed (for my understanding) Which, if you are organized, you already have in $notes_dir/$hostname/install.md as something that looks like this: ``` sudo sfdisk /dev/sdX < The partitions table of my HDD is part of my backup. Cheers, -- Franco Martelli
Re: To partition or not to partition MD arrays (Was Re: smartctl cannotaccess my storage, need syntax help)
Franco Martelli (12024-01-19): > > One case against using partitions on mdraid: if your array gets messed > > up, you get to recreate those partition tables yourself and that's just > > hilarious if you don't have a backup. Happened to a friend of mine, > > reason was a UPS brownout. > How can I get a backup of mdadm RAID partition? You do not need a backup of the RAID partitions, that would be terribly inefficient. You need a backup of the partition table. Which, if you are organized, you already have in $notes_dir/$hostname/install.md as something that looks like this: ``` sudo sfdisk /dev/sdX < signature.asc Description: PGP signature
Re: To partition or not to partition MD arrays (Was Re: smartctl cannotaccess my storage, need syntax help)
On 19/01/24 at 09:03, Anssi Saari wrote: One case against using partitions on mdraid: if your array gets messed up, you get to recreate those partition tables yourself and that's just hilarious if you don't have a backup. Happened to a friend of mine, reason was a UPS brownout. How can I get a backup of mdadm RAID partition? And which tool to backup the whole disks of an array? The only tool that it comes in mind it is "dd" that it isn't a viable solution for me. I think is useless to backup the raw data stored in a partition or the whole disk. I backup files and directories stored in the filesystem not raw data. If an error occurs in the RAID, mdadm takes care to warn me via email... I hope! I think he scanned his disks for copies of the superblock but didn't find any and then somehow with a lot of hassle eventually figured out what the partition tables were. So in a catastrophe, partition tables are one more obstacle to cross before you can start actually recovering your data. Me too ran into a catastrophe scenario, I had lost /dev/md0, the reason was using hibernate (suspend to disk) in a logical volume placed inside the RAID. I think it was damaged the RAID metadata. I got rid of this using Debian-installer, I thought that I had loosed everything and I prepared for reinstall, when Debian-installer asked me to create the new RAID I specify all the four partitions, I saved, and magically the logical device and all my logical volumes, embedded in the old RAID, reappeared. To partition was not a trouble in those circumstances. My only mdraid was on raw partitions but that never had any issues. I think zfs effectively does the same, no partitions. Which raw partitions? Maybe did you mean without partitions? I never used zfs it's full featured, I prefer to keep the things simple: RAID -> LVM -> ext4 Cheers, -- Franco Martelli
Re: To partition or not to partition MD arrays (Was Re: smartctl cannotaccess my storage, need syntax help)
Hi, On Thu, Jan 18, 2024 at 10:28:30AM -0600, Nicholas Geovanis wrote: > Sounds like this group has finally achieved a long overdue consensus. How > many times since LVM was ready for root/boot volumes have I been told that > using partitions was necessary good practice. Even had that in job > interviews, where half the team would grin at me saying it and the other > half scowling at my "poor practice". > > Now we know it was just personal preference all along. Like somebody said > :-) Look, if you're going to resolve this thread so quickly all it means is that someone is going to have to mention home.arpa or their time zone setting again. We have strict quotas here for the amount of circular repeating "you don't do things like me therefore you are wrong and here are a selection of Internet standards to back me up" threads that must be taking place at once. 😀 Thanks, Andy -- https://bitfolk.com/ -- No-nonsense VPS hosting
Re: To partition or not to partition MD arrays (Was Re: smartctl cannotaccess my storage, need syntax help)
On Wed, Jan 17, 2024, 9:35 PM gene heskett wrote: > On 1/17/24 19:54, Steve McIntyre wrote: > > Andy Smith wrote: > ... > >> Then there will just be people going by taste. > >> > >> Personally I still put them directly on drives. If I ever get taken > >> out by one of those crappy motherboards, I reserve the right to get > >> a different religion. 😀 > > > > I'm clearly a member of a third group of people,,, :-) > > > > Putting partitions on the RAID drives helps *me* identify them. > > > you aren't alone Steve. > Cheers, Gene Heskett. > Sounds like this group has finally achieved a long overdue consensus. How many times since LVM was ready for root/boot volumes have I been told that using partitions was necessary good practice. Even had that in job interviews, where half the team would grin at me saying it and the other half scowling at my "poor practice". Now we know it was just personal preference all along. Like somebody said :-) >
Re: To partition or not to partition MD arrays (Was Re: smartctl cannotaccess my storage, need syntax help)
On 1/17/24 19:54, Steve McIntyre wrote: Andy Smith wrote: The newer set of people recommending partitions are mostly doing so because there's been a few incidents of "helpful" PC motherboards detecting on boot what they think is a corrupt GPT, and replacing it with a blank one, damaging the RAID. This is a real thing that has happened to more than one person; it even got linked on Hacker News I believe. Then there will just be people going by taste. Personally I still put them directly on drives. If I ever get taken out by one of those crappy motherboards, I reserve the right to get a different religion. 😀 I'm clearly a member of a third group of people,,, :-) Putting partitions on the RAID drives helps *me* identify them. you aren't alone Steve. Cheers, Gene Heskett. -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis
