On 01/11/2023 01:33 PM, H wrote:> On 01/11/2023 02:09 AM, Simon Matter wrote: >> 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. >> >> > But is your strategy of dividing the large disk into individual RAID1 arrays also applicable to SSDs? I have heard, perhaps incorrectly, that once a SSD fails, the entire SSD becomes unusable which would suggest that dividing it into multiple RAID1 arrays would not be useful? >Follow-up question: Is my proposed strategy below correct: - Make a copy of all existing directories and files on the current disk using clonezilla. - Install the new M.2 SSDs. - Partitioning the new SSDs for RAID1 using an external tool. - Doing a minimal installation of C7 and mdraid. - If choosing three RAID partitions, one for /boot, one for /boot/efi and the third one for the rest, do I go with the default mdraid version, ie 1.2 I believe? - Copying the backup above with contents of the the existing disks, ie not just /root and /home but all other directories and files to the new disks from the clonezilla backup. Note that the new disks will be larger. - Change the boot sequence in the BIOS and reboot. Thanks.
> On 01/11/2023 01:33 PM, H wrote: >> On 01/11/2023 02:09 AM, Simon Matter wrote: >>> 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. >>> >>> >> But is your strategy of dividing the large disk into individual RAID1 >> arrays also applicable to SSDs? I have heard, perhaps incorrectly, that >> once a SSD fails, the entire SSD becomes unusable which would suggest >> that dividing it into multiple RAID1 arrays would not be useful? >> > Follow-up question: Is my proposed strategy below correct: > > - Make a copy of all existing directories and files on the current disk > using clonezilla. > > - Install the new M.2 SSDs. > > - Partitioning the new SSDs for RAID1 using an external tool. > > - Doing a minimal installation of C7 and mdraid. > > - If choosing three RAID partitions, one for /boot, one for /boot/efi and > the third one for the rest, do I go with the default mdraid version, ie > 1.2 I believe?I think at least /boot/efi must be on an mdraid version which has its metadata at the end of the partition, I'm not sure about /boot. That said, I think the installer should take care here but I'm not sure it already does on C7.> > - Copying the backup above with contents of the the existing disks, ie not > just /root and /home but all other directories and files to the new disks > from the clonezilla backup. Note that the new disks will be larger.I can't comment on clonezilla as I've never used it. Tar and rsync are my friends when doing such things. I think you may have to take special care for boot related stuff like things in /boot and boot/efi. The other thing to care is for hardware related stuff like UUIDs generated in /etc/udev. The whole undertaking is not trivial.> > - Change the boot sequence in the BIOS and reboot.That's EFI, yes? I still fell like a greenhorn with EFI :) Regards, Simon
> Follow-up question: Is my proposed strategy below correct: > - Make a copy of all existing directories and files on the current disk using clonezilla. > - Install the new M.2 SSDs. > - Partitioning the new SSDs for RAID1 using an external tool. > - Doing a minimal installation of C7 and mdraid. > - If choosing three RAID partitions, one for /boot, one for /boot/efi and the third one for the rest, do I go with the default mdraid version, ie 1.2 I believe? > - Copying the backup above with contents of the the existing disks, ie not just /root and /home but all other directories and files to the new disks from the clonezilla backup. Note that the new disks will be larger. > - Change the boot sequence in the BIOS and reboot.I don't know if this is still a problem, but in the past, CentOS was only writing the boot-loader on one of the RAID-disks. If this one would fail, the OS would not boot. So you had to make sure to copy the boot-loader onto all RAID-members. Michael