mass-storage/mass-storage-backup-archive.md

@@ -68,7 +68,7 @@ library will be moved there, so that the 2 copies will be in different locations
 **Which type of files can be sent to the offline archiving system?**  
 Tape libraries are designed for long term storage of data. They are more stable 
 and a lot cheaper than disk space. However, they are also slower in term of writing/reading 
-capacity, so retrieving archived data can take up to a week. 
+capacity, so retrieving archived data can take several days. 
 Therefore, files sent to the offline archiving system should be files that the user 
 needs to keep (for legal reasons for example, or data that have been fully analyzed but not 
 published yet, in case a reviewer is asking to redo part of the analysis with a 
@@ -80,11 +80,24 @@ new software or different options) but do not need to use/access quickly anymore
 please organize the main folder into subfolders containing data that are likely to be retrieved 
 together and keep a record of the tree structure, so that we don't need to retrieve
 the whole archive if you need only some of the files.  
-   - Given that the process to archive and restore data is quite laborious, the minimum 
-size you can send to archive is 500Gb. If your experiments typically generate less 
+   - The minimum size you can send to archive is 500Gb. If your experiments typically generate less 
 than 500Gb of data, you can wait to have several experiments (eventually in separated subfolder) 
 before to archive them. 
 
+**Warning about hardlinks**  
+NB1: If you don't know what a hardlink is, you probably don't have any (it's actually quite rare to have some in data).
+NB2: If you made links using `ln -s` command, you made a softlinks and not a hardlink.
+If you have some hardlinks in your archive folder and if other occurrences of the same file are in your project folder, 
+be aware that once the file will be truncated, it will be so in all locations 
+(everywhere where you have a hardlink pointing to that file). 
+The side effect of this is that if you open the copy in your project folder, 
+the file will be restored on disk, which means that 
+1. you need to have enough space in the folder to store it (or the retrieve will fail)
+2. opening it the first time will be very slow
+
+Don't hesitate to ask the bioinformatic teams if you have any question or want to 
+discuss your specific utilisation of hardlinks.
+
 **NB:** In some circumstances, some files may be sent offline even if the user didn't ask for it. 
 See the [automatic archiving](mass-storage/mass-storage-backup-archive#automatic-archiving) for more information.
 
@@ -106,7 +119,11 @@ your team folder on the mass storage. This need to be done only the very first t
     - Numerous small files (typically thousands of files smaller than 4Mb) are grouped into archive files as explained [here](mass-storage/mass-storage-compression)
 3. Create a subfolder in the "ARCHIVE" folder with a meaningful name (for example the name of the project, the date and any specific information).   
 **WARNING: don't use any space or special character in the folder names !!!!**
-4. Move in that folder the data you want to send for archiving (organised as described above) 
+4. Move in that folder the data you want to send for archiving (organised as described above)  
+**WARNING:** if your data are on the mass storage it's very important to move them (using `mv` and not rsync or cp)!!!   
+This move should be done directly on the mass storage (see important considerations below) and not from the cluster.  
+If you want to archive data that are currently on another disk (for example gallia or CECI cluster), you need to 
+transfer them using rsync or cp/scp.
 5. Wait until you have at least 500Gb of data to send for archiving 
 (eventually grouping separated project in separated sub-folder). 
 6. Keep a record of what you have sent for archiving, for example in a text file explaining what's in each folder. 
@@ -123,7 +140,13 @@ Once that's done, you won't be able to enter the archived folder and to see your
 
 
 **IMPORTANT CONSIDERATIONS**
-- Moving data to the "ARCHIVE" folder is not enough for them to be truncated. 
+- To move your data to the "ARCHIVES" folder, it's recommended to log into the mass storage with 
+`ssh u123456@massstorage.giga.priv` (replace u123456 by your university userID). 
+Then you should run a `screen` session to prevent any interruption of the transfer 
+if you lose your connection to the mass storage.
+If you don't know how to run a screen session or move file from a terminal or if you are not sure 
+of the method you should use, please contact the bioinformatic team.
+- Moving data to the "ARCHIVES" folder is not enough for them to be truncated. 
 You have to ask the UDIMED/UDIGIGA to archive them. 
 Data in the "ARCHIVE" folder that haven't been truncated still takes up space on disk and are therefore 
 still taken into account for the billing of your disk usage.