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Replace a failed drive in Linux RAID

I have a server that had 2 250 gig drives setup in a RAID 1. I have installed 2 tera byte drives but the RAID will not expand to use the space. I have tried all kinds of stuff, anyone know how to expand the partition? I only have 3 partitions, Boot, Swap and Ext3 for the data.

1 expand partitions
2 expand raid
3 expand lvm if you use it
4 expand filesystems

Step 1 determines how much each expands, so careful with that. Parted is the best tool for that step. If you are lucky or have planned ahead, you don't expand boot and swap and ext3 is the last one so there is no need to move stuff around and even fdisk would suffice, just change the end of last partition to the end of the disk.

I have tried to use G-parted to expand the partition, but it sees it as a linux RAID and will not do anything with it. I guess this is where I am stuck. I make a full backup with clonezilla before I do anything so I can always blast it back if I screw it up.

Great article Vincent! RAID 1 is the best configuration for redundancy and BCP. We see RAID 0/1/5/10 Arrays come in at http://www.24hourdata.com all the time. Companies and Users that have RAID 1 in place always get their data back and pay much less money. Most people do not understand the most RAID levels are built for fault tolerance not redundancy.

Consider RAID 5 and hot swap drives and you can really minimize down time.

Thanks for the info, I have been really stressing about this.

that the problem I have with linux RAID, basic operation require you to read or document an range of obscure commands.

Even software RAID bios (like SI or Intel) have dead simple interfaces running. (how about some kernel modules to work with onboard "fake" RAID.)

If Linux want larger acceptance, they really need to make sysadmins lives easier, not harder. There is so much room for error in those commands, I would never dare attempting it with drives containing company data

If a hard drive failed on one of my windows boxes, or on a linux box with hardware RAID, I would yank the broken drive, stick in the new one and hit the rebuild button, its really that simple.

Until they can make it even close to that simple, I will stick with hardware RAID for linux boxes. At least they took the time to make the sysadmin's life easier.

It is not really Linux which is difficult, it is partitioning and LVM, but you don't really need those in most cases. I try to use whole disks without any partitions in RAID5/6 arrays and then it is just to remove the disk, replace and add, or if there is a hot spare, that can wait for a later time. The only command you need is mdadm and some program like smartctl which displays drive serial numbers and a note with failed and replacement drive serials.

For bootable disks that recipe isn't so good, but if you avoid logical partitions, it makes life a bit easier. That way copying just the first 16 (boot record + partition table + grub 1. stage) sectors with dd booted from live CD/USB stick to the replacement drive would be enough as a preparation and then just regular boot from the hard drive. This assumes you have RAID1.

I don't much mind complexity even if I try to avoid it, but the flexibility and reliability of SW RAID is much better than with HW RAID. mdadm can now grow with bigger devices or more devices and even convert RAID-5 to RAID-6. I doubt any HW RAID can do those. I am currently exploring ZFS and zpool (on OpenSolaris) and it has features like instant construction of raidz? arrays (raidz is like RAID-5, raidz2 like RAID-6 and raidz3 might some day have RAID-7 as equivalent), which need co-op of file system and raid software and a separate RAID will never be that smart. Mdadm is separate and a construction of a RAID array with parity takes ages even if it runs on background. Brtfs on Linux is going the same direction as ZFS with integrated RAID. Guess what Sun recommends with ZFS? Use whole disks, no partitions or slices.

It appears that you are incredibly misinformed about HW RAID, or perhaps your experience with HW RAID was with some lousy controllers. You need to understand that there are pros and cons to SW / HW RAID. HW RAID has higher initial cost, but most large enterprise environments see the benefits of HW RAID overwhelmingly outweighing the initial cost, and more to the point, the performance and reliability benefits over SW RAID. If SW RAID were so much better than HW RAID, then most large enterprise environments would be running SW RAID, period. The fact is, the overwhelming majority of large, enterprise environments run HW RAID, and they are not doing it because they don't understand SW RAID. Instead, large enterprise environments use HW RAID because they know it offers better system performance, better reliability, and the most flexibility.

Oh, and my Intel HW RAID controllers can convert a RAID-5 array to RAID-6 just fine, and will do it much faster than your SW RAID. Of course, the high-performance HW RAID controllers I use are not the RAID controllers you typically find at your local retail shops. Based on my experience with numerous, large IT environments, the HW RAID controllers I use and work with are among the best available (Intel, LSI, Adaptec, etc.), and my experience (as well as experience from any of my colleagues) with HW RAID does not reconcile with your nonsense about HW RAID.

On a side note, as if there was not already enough long-standing problems with RAID-5, when you begin to consider large hard drives currently ranging from 1TB - 2TB these days (and they certainly are not going to be getting smaller), it is easy to argue that RAID-5 should never be used in the first place, due to the likelihood of a drive failure, followed by another failure during a rebuild.


Friends don't let friends use RAID-5!
http://www.miracleas.com/BAARF/BAARF_members_sql.php

http://www.miracleas.com/BAARF/RAID5_versus_RAID10.txt

Software raid only provides redundant disks. Hardware raid can provide redundant controllers so that if you lose a controller your array continues to function. SW RAID requires a boot sector that is a non raid sector. If that drive or sector gets corrupted then your machine will no longer boot, but with HW raid your machine will still boot no matter which of the redundant drives is corrupted.

Bill

Your statement that SW RAID requires a non-RAID boot sector is not correct. I build my systems entirely on RAID 1 pairs -- boot, swap, OS, data, etc. -- everything. (My data drives are LVM partitions that sit on top of the RAID md's.)

And while I don't agree with the arrogant attitude of the 'guy from Redmond', I do agree that the day & age of RAID 5 is long over. Disks are cheap enough to spend a few more dollars to double up on everything. Cost no longer justifies making your system do gyrations to maintain a parity slice so that you can get away with "only buying one additional drive". KISS applies here.

Aside from reducing system load and disk wear & tear, you have the ability to remove a RAID 1 drive and put it another system and run. You have no hope doing that with RAID 5. (Makes cloning a system VERY easy.)

I am merely stating facts. Just because you don't like them, or how I presented them, doesn't make me arrogant. So please, keep your name calling to yourself.