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| services:cluster:usetmpforio [2015/12/11 21:23] – created dreger | services:cluster:usetmpforio [2024/04/26 14:19] (current) – hoffmac00 |
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| ====== Use /tmp for I/O intensive single node jobs ====== | ====== Use /tmp for I/O intensive single node jobs ====== |
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| Jobs that do a lot of I/O operations on a shared cluster filesystem like ''/scratch'' can severely slow down the whole system. If your job does not use multiple nodes and is not reading and writing very large files, it might be a good idea to move input and output files to the ''/tmp'' folder on the compute node itself. ''/tmp'' is a RAM based filesystem, meaning that anything you store there is actually stored in memory. So space is quite limited. Currently you can use at most 24GB of ''/tmp'' space. Since ''/tmp'' uses RAM, usage also counts towards the allocated memory limit (e.g. --mem or --mem-per-cpu settings). So the memory that the process uses during calculation plus the amount of data stored in files below /tmp can not exceed the total amount of RAM installed in the compute node. Let's look at some examples... | Jobs that do a lot of I/O operations on a shared cluster filesystem like ''/scratch'' can severely slow down the whole system. If your job does not use multiple nodes and is not reading and writing very large files, it might be a good idea to move input and output files to the ''/tmp'' folder on the compute node itself. |
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| ===== Please note: usable space below /tmp is limited by the --mem option ===== | ''/tmp'' is a RAM based filesystem, meaning that anything you store there is actually stored in memory. So space is quite limited. Currently all jobs on a node can use at most 20% of the total system memory for space in ''/tmp''. If you need more space, you should consider using ''/dev/shm'', where you can use up to 50% of the total system memory per job. |
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| <xterm> | |
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| </xterm> | <note important> |
| | Usable space below /tmp and /dev/shm counts towards your job's memory usage and thus is limited by the ''--mem'' option |
| | </note> |
