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abstract:caviness:filesystems:lustre [2020-03-06 09:43] – [The Lustre Filesystem] anita | abstract:caviness:filesystems:lustre [2020-05-29 12:21] – frey |
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With four disks being used in parallel (example (b) above), the block writing overlaps and takes just 8 cycles to complete. | With four disks being used in parallel (example (b) above), the block writing overlaps and takes just 8 cycles to complete. |
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Parallel use of multiple disks is the key behind many higher-performance disk technologies. RAID (Redundant Array of Independent Disks) level 6 uses three or more disks to improve i/o performance while retaining //parity// copies of data((The two parity copies in RAID-6 imply that given //N// 2 TB disks, only //N-2// actually store data. E.g. a three disk RAID-6 volume has a capacity of 2 TB.)). Should one or two of the constituent disks fail, the missing data can be reconstructed using the parity copies. It is RAID-6 that forms the basic building block of the Lustre filesystem on the Mills cluster. | Parallel use of multiple disks is the key behind many higher-performance disk technologies. RAID (Redundant Array of Independent Disks) level 6 uses three or more disks to improve i/o performance while retaining //parity// copies of data((The two parity copies in RAID-6 imply that given //N// 2 TB disks, only //N-2// actually store data. E.g. a three disk RAID-6 volume has a capacity of 2 TB.)). Should one or two of the constituent disks fail, the missing data can be reconstructed using the parity copies. It is RAID-6 that forms the basic building block of the Lustre filesystem on our clusters. |
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===== A Storage Node ===== | ===== A Storage Node ===== |
For example, the Mills cluster contains five //storage appliances// that each contain many hard disks. For example, ''storage1'' contains 36 SATA hard disks (2 TB each) arranged as six 8 TB RAID-6 units: | For example, the Mills cluster contains five //storage appliances// that each contain many hard disks. For example, ''storage1'' contains 36 SATA hard disks (2 TB each) arranged as six 8 TB RAID-6 units: |
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{{ osts.png |Example image of the Mills storage1 appliance.}} | {{ :abstract:caviness:filesystems:caviness-lustre-oss_ost.png?400 |Example image of Caviness Lustre OSS/OST. }} |
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Each of the six OST (Object Storage Target) units can survive the concurrent failure of one or two hard disks at the expense of storage space: the raw capacity of ''storage1'' is 72 TB, but the data resilience afforded by RAID-6 costs a full third of that capacity (leaving 48 TB). | Each of the six OST (Object Storage Target) units can survive the concurrent failure of one or two hard disks at the expense of storage space: the raw capacity of ''storage1'' is 72 TB, but the data resilience afforded by RAID-6 costs a full third of that capacity (leaving 48 TB). |