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?
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 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?What you heard seems extremely oversimplified to me. A HD can fail in different manners and so can SSDs. Anyway, the splitting of large disks has additional advantages. Think of what happens in case of a failure (power loss, kernel crash...). With the disk as one large chunk, the whole disk has to be resynced on restart while with smaller segments only those which are marked as dirty have to be resynced. This can make a bit difference. Regards, Simon