[CentOS] Upgrading system from non-RAID to RAID1

Wed Jan 11 13:34:02 UTC 2023
Robert Moskowitz <rgm at htt-consult.com>

On 1/11/23 02:09, Simon Matter wrote:
>> I plan to upgrade an existing C7 computer which currently has one 256 GB
>> SSD to use mdadmin software RAID1 after adding two 4 TB M2. SSDs, the rest
>> of the system remaining the same. The system also has one additional
>> internal and one external harddisk but these should not be touched. The
>> system will continue to run C7.
.... trimming
>> - I do not see any benefit to breaking up the LVM2/LUKS partition
>> containing /root, /swap and /home into more than one RAID1 partition or am
>> I wrong? If the SSD fails, the entire SSD would fail and break the system,
>> hence I might as well keep it as one single RAID1 partition, or?
> What I usually do is this: "cut" the large disk into several pieces of
> equal size and create individual RAID1 arrays. Then add them as LVM PVs to
> one large VG. The advantage is that with one error on one disk, you wont
> lose redundancy on the whole RAID mirror but only on a partial segment.
> You can even lose another segment with an error on the other disk and
> still have redundancy if the error is in another part.
> That said, it's a bit more work to setup but has helped me several times
> in the decades ago.

Ah, now I begin to get it.  Separate partitions RAIDed.

>> - Is the next step after the RAID1 partitioning above then to do a minimal
>> install of C7 followed by using clonezilla to restoring the LVM2/LUKS
>> partition??
>> - Any advice on using clonezilla? Or the external partitioning tool?
>>   - Finally, since these new SSDs are huge, perhaps I should take the
>> opportunity to increase the space for both /root and /swap?
>> - /root is 50 GB - should I increase it to eg 100 GB?
>> - The system currently has 32 GB of memory but I will likely upgrade it to
>> 64 GB (or even 128 GB), perhaps I should at this time already increase the
>> /swap space to 64 GB/128 GB?
> I'm also interested here to learn what others are doing in higher memory
> situations. I have some systems with half a TB memory and never configured
> more than 16GB of swap. I has usually worked well and when a system
> started to use swap heavily, there was something really wrong in an
> application and had to be fixed there. Additionally we've tuned the kernel
> VM settings so that it didn't want to swap too much. Because swapping was
> always slow anyway even on fast U.2 NVME SSD storage.

Perhaps you have not dealt with Firefox?  :)

On my Fedora 35 notebook, it slowly gobbles memory and I have to quit it 
after some number of days and restart.

Now I only have 16GB of memory, 16GB physical swap, and 8GB zram swap.

Building a F37 system now and see how that works, I doubt there is any 
improved behavior with Firefox.

> Regards,
> Simon
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> https://lists.centos.org/mailman/listinfo/centos