| Both sides previous revision Previous revision Next revision | Previous revision Next revisionBoth sides next revision |
| abstract:caviness:filesystems:lustre [2020-03-06 09:42] – [The Lustre Filesystem] anita | abstract:caviness:filesystems:lustre [2020-03-06 09:47] – [All About Lustre] anita |
|---|
| 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. |
| |
| 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. |
| |
| ===== A Storage Node ===== | ===== A Storage Node ===== |
| * File system capacity is not limited by hard disk size | * File system capacity is not limited by hard disk size |
| |
| The capacity of a Lustre filesystem is the sum of its constituent OSTs, so a Lustre filesystem's capacity can be grown by the addition of OSTs (and possibly OSSs to serve them). For example, should the 172 TB Lustre filesystem begin to approach its capacity, additional capacity could be added with zero downtime by buying and installing another OSS pair. | The capacity of a Lustre filesystem is the sum of its constituent OSTs, so a Lustre filesystem's capacity can be grown by the addition of OSTs (and possibly OSSs to serve them). For example, should the 172 TB Lustre filesystem begins to reach its capacity, additional capacity could be added with zero downtime by buying and installing another OSS pair. |
| |
| <note important>Creating extremely large filesystems has one drawback: traversing the filesystem takes so much time that it becomes impossible to create off-site backups for further data resilience. For this reason Lustre filesystems are most often treated as volatile/scratch storage.</note> | <note important>Creating extremely large filesystems has one drawback: traversing the filesystem takes so much time that it becomes impossible to create off-site backups for further data resilience. For this reason Lustre filesystems are most often treated as volatile/scratch storage.</note> |