Re: HELP! Re: How to fix I/O errors? (SOLVED)
On 02/12/2017 01:59 PM, Marc Shapiro wrote:
> On 02/12/2017 08:30 AM, Marc Auslander wrote:
>> I do not use LVM over raid 1. I think it can be made to work,
>> although IIRC booting from an LVM over RAID partion has caused issues.
> my boot partitions are separate. They are not under LVM.
>> LVM is useful when space requirements are changing over time and the
>> ability to add additional disks and grow logical partions is needed.
>> In my case, that isn't an issue. I have only a small number of
>> paritions - 3 because of history but starting from scratch, I'd only
>> have two - root (including boot) and /home.
> I started using LVM when I had a much smaller disk (40GB). With the current
> 1TB disk, even with three accounts on the box, and expanding several
> partitions when moving to the new disk, I have still partitioned less than
> half the disk and that is less than 1/3 used. So, no, LVM is probably not an
> issue any more.
>
> BTW, what is your third partition, and why would you not separate it now if
> starting from scratch?
>> I converted to mdamd raid as follows, IIRC.
>>
>> Install the second disk, and parition it the way I wanted.
>> Create a one disk raid 1 partion in each of the new paritions.
>> Take down my system, boot a live system from CD, and use a reliable
>> copy program like rsync to copy each of the partitions contents to the
>> equivalent raid partition.
>> Run grub to set the new disk as bootable. This is by far the
>> trickiest part.
>> Boot the new system and verify it's happy.
>> Repartion the now spare disk to match the new one if necessary.
>> You may need to zero the front of each partion with dd if=/dev/zero
>> to avoid mdadm error checks.
>> Add the partitions from that disk to the mdadm paritions and let mdadm
>> do its thing.
>>
> On 02/12/2017 07:08 AM, Bob Weber wrote:
>>
>> I use raid 1 also for the redundancy it provides. If I need a backup I just
>> connect a disk, grow each array and add it to the array (I have 3 arrays for
>> /, /home and swap). It syncs up in a couple hours (depending on size of the
>> array). If you have grub install itself on the added disk you have a
>> bootable copy of your system (mdadm will complain about a degraded array). I
>> then remove the drive and place it in another outbuilding in case of fire.
>> You can even use a external USB disk housing for the drive to keep from
>> shutting down the system. The sync is MUCH slower ... just coma back the
>> next day and you will have your backup. You then grow each array back to the
>> number of disks you had before and all is happy again. Note that this single
>> disk backup will only work with raid 1.
>>
> So, how do you do a complete restore from backup? Boot from just the single
> backup drive and add additional drives as Marc Auslander describes, above?
Yes if that is what you need to do if there was a complete failure in your
machine and maybe you had to start over with a new motherboard and power supply.
>
>
> One other question. If using raid, how do you know when a disk is starting to
> have trouble, as mine did? Since the whole purpose of raid is to keep the
> system up and running I wouldn't expect errors to pop up like I was getting.
> Do you have to keep an eye on log files? Which ones? Or is there some other
> way that mdadm provides notification of errors? I've got to admit, even
> though I have been using Debian for 18 or 19 years (since Bo), log files have
> never been my favorite thing. I generally only look at them when I have a
> problem and someone on this luist tells me what to look for and where.
>
> Marc
>
>
I use a program called ossec. It watches logs of all my linux boxes so I get
email messages about disk problems. I also do periodic self tests on all my
drives controlled by smartd from the smartmontools package. I also use a
package called logwatch which summarizes my logs. The messages from mdadm and
smartd are seen by ossec. When I mess with an array to make it larger and add a
disk for backup I get the messages in my mailbox about a degraded array. As I'm
reading them I am startled until I remember ...Oh I did that! I have a daily
cron job that emails the output of "smartctl -a /dev/sdx" for each drive on each
machine so I can keep a history of the parameters for each drive.
I also use backuppc on a dedicated server to backup all my boxes. That way I
can get back files I deleted by mistake or modified and has to go back to a
previous version. I now have all my machines on raid 1, My wife just recently
gave up on Win 10 with all those updates that just took over her machine when
Windows wanted to! So now she is running Debian/KDE.
After writing this I wonder if I am over doing this. I just don't want to loose
data from a failing drive. I lived through 3.5 inch floppies which seemed to
always fail. And tape drives that were painfully slow. Not to mention back in
the mid 70s saving Z80 programs and data to audio cassette tapes at 1200 baud!
I was so glad to get my first 8 inch floppys working.
...Bob
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