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On Monday, 24 June 2019 18:00:29 BST Peter Humphrey wrote: |
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> On Monday, 24 June 2019 16:59:08 BST Grant Taylor wrote: |
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> > > On this box, which does need lvm for RAID-1 on two SSDs: |
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> > Do you /need/ LVM? Or is it extra that comes with device-mapper? |
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> |
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> No, I do actually use lvm to base a raid-1 file system on. I haven't |
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> considered raid-1 without lvm; is that feasible? |
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Almost totally. They two are separate functions with synergistic interaction. |
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RAID 1 offers redundancy by mirroring data between two block devices. LVM |
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offers a flexible partitioning scheme where you can add space, move, snapshot, |
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etc. data using a logical software layer to manage their storage across |
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partitions and physical disks. I've put together RAID 1 disks with no LVM and |
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used LVM with no RAID. |
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NOTE: To confuse things you can instead use LVM's built in 'RAID |
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functionality' - see below. |
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I recall reading somewhere that SSDs are better used with LVM's natively |
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configured RAID functionality, rather than a separate RAID layer, which in a |
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mirrored RAID it will cause accelerated wear due to the way RAID metadata are |
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mirrored between block devices. I don't think I've ever used LVM's RAID |
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capability, but it would probably boil down to running: |
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lvcreate --mirrors 1 --type raid 1 -n LV_myRAID VG_blah-blah |
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Others more knowledgeable in these technologies could chime in to correct me |
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no doubt. |
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PS. LVM-RAID uses the kernel's mdraid, but with less tools to manage the RAID |
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configuration than mdadm offers: |
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https://unix.stackexchange.com/questions/150644/raiding-with-lvm-vs-mdraid-pros-and-cons |
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-- |
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Regards, |
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Mick |
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