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services:computing:hpc [2020/11/25 14:38]
Piero Calucci [Simplest possible job]
services:computing:hpc [2021/09/06 12:13] (current)
Piero Calucci [Hardware and Software]
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-Ulysses v2 can be accessed ​via the login nodes at ''​frontend1.hpc.sissa.it''​ or ''​frontend2.hpc.sissa.it''​ from SISSA network or from SISSA [[:​vpn|VPN]]. More access options might be made available in due time.+SSH access to Ulysses v2 is provided ​via the login nodes at ''​frontend1.hpc.sissa.it''​ or ''​frontend2.hpc.sissa.it''​ from SISSA network or from SISSA [[:​vpn|VPN]]. More access options might be made available in due time.
  
 ===== Hardware and Software ===== ===== Hardware and Software =====
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 The software tree is the same you have on Linux workstations,​ with the same [[services:​modules|Lmod modules]] system (with the only exception of desktop-oriented software packages). The software tree is the same you have on Linux workstations,​ with the same [[services:​modules|Lmod modules]] system (with the only exception of desktop-oriented software packages).
 +
 +A small number of POWER9-based nodes are also available (2 sockets, 16 cores, 4 threads per core; 256GB RAM) with 2 or 4 Tesla V100. Please note that you cannot run x86 code on POWER9. For an interactive shell on a P9 machine, please type ''​p9login''​ on frontend[12].
  
 ===== Queue System =====  ===== Queue System ===== 
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   * **''​long1''​** and **''​long2''​**:​ max 8 nodes, max 48h   * **''​long1''​** and **''​long2''​**:​ max 8 nodes, max 48h
   * **''​gpu1''​** and **''​gpu2''​**:​ max 4 nodes, max 12h   * **''​gpu1''​** and **''​gpu2''​**:​ max 4 nodes, max 12h
 +  * **''​power9''​**:​ max 2 nodes, max 24h
  
 <note tip>​Please note that hyperthreading is enabled on all nodes (it was disabled on old Ulysses). If you **do not** want to use hyperthreading,​ the ''​%%--hint=nomultithread%%''​ options to srun/sbatch will help. <note tip>​Please note that hyperthreading is enabled on all nodes (it was disabled on old Ulysses). If you **do not** want to use hyperthreading,​ the ''​%%--hint=nomultithread%%''​ options to srun/sbatch will help.
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 Hello, World! Hello, World!
 </​code>​ </​code>​
 +
 +<note warning>​Please note that MPI jobs are only supported if they allocate all available core/​threads on each node (so 20c/40t on *1 partitions and 32c/64t on *2 partitions. In this context, //not supported// means that jobs using fewer cores/​threads than available may or may not work, depending on how cores //not// allocated to your job are used.</​note>​
 +===== Filesystem Usage and Backup Policy =====
 +
 +''/​home''​ and ''/​scratch''​ are both general-purpose filesystems,​ they are based on the same hardware and provide the same performance level. When you first login on Ulysses, ''/​home/​$USER''​ comes pre-populated with a small number of files that provide some reasonable configuration defaults. At the same time, ''/​scratch/​$USER''​ is created for you where you have write permission.
 +
 +Default quotas are 200GB on ''/​home''​ and 5TB on ''/​scratch'';​ short-term users (e.g. accounts created for workshops, summer schools and other events, that usually expire in a matter of weeks) are usually given smaller quotas in agreement with workshop organizers. On special and motivated request a larger quota can be granted: please write to [[helpdesk-hpc@sissa.it]],​ Cc: your supervisor (if applicable) with your request; please note that the storage resource is limited, and not every request can be granted.
 +
 +<note tip> **Frequently Asked Question: what does "​quota"​ mean, exactly?​** ​
 +  * Quota is the traditional Unix word for and administrative limit imposed upon the usage of a certain resource. In this context, a "5TB quota" means that you will not be allowed to write more than that in a given filesystem, even if free space is available. It does not mean that those 5TB are reserved for you and are always available. At this time, filesystem quotas are enforced only on total used space; it is possible that in some future quotas are enabled on the number of files too.
 +  * A ''​quota''​ command is available and will give you a summary of your filesystem usage.
 +  * Please note that filesystem space is allocated in blocks, so the actual space usage can be different from the apparent file size. Currently the smallest possible block allocation is 4kB, so when computing quota usage file sizes are rounded up to the next 4kB multiple. "''​ls -s ...''"​ will report the actual allocated space for your files instead of (or along side with, depending on the command line) their apparent size.
 +</​note>​
 +
 +Daily backups are taken of ''/​home'',​ while no backup is available for ''/​scratch''​. If you need to recover some deleted or damaged file from a backup set, please write to [[helpdesk-hpc@sissa.it]]. Daily backups are kept for one week, a weekly backup is kept for one month, and monthly backups are kept for one year.
 +
 +Due to their inherent volatility, some directories can be excluded from the backup set. At this time, the list of excluded directories includes only one item, namely ''/​home/​$USER/​.cache'' ​
 +
 ===== Reporting Issues ===== ===== Reporting Issues =====