There are 4 dCache installations available in LIT, of which 3 work according to the rules and conventions accepted in WLCG, two of which are for VO CMS only. Discussion of work with these systems is not included in this manual.

One system is allocated for users registered on LIT farms and VOs not part of WLCG. These include, for example, MPD, BES, Biomed and others.

At present, this system is single-level, i.e. the amount of data stored in it is limited to reasonable limits. These limits are a few tens of TB, establishes the leadership of LIT when allocating space for a new VO.

Tree of names.

Regardless of whether the user is allocated a place within the VO framework, or he works independently, the user must register at the LIT farm. There he receives an identifier, which is referred to below as <login>. For example, trofimov – Trofimov’s login.

Registered users get access to files or in a subdirectory

/pnfs/jinr.ru/data/user/<the first letter of the login> / <login>

Therefore, the trofimov user files are stored in the

/pnfs/jinr.ru/data/user/t/trofimov

If trofimov worked in VO TVV, then the files would be in the directory /pnfs/jinr.ru/data/tvv…, and then how VO will place them there.

Features of access to files.

Files in dCache are written once, and are read many times. Modification is not allowed. The process of changing the contents of a file looks like this:

Move the file from the dCache space to the local;
Change the file;
Erase the file from dCache;
Write the file from the local space to the dCache space under the old name.

Access is exclusively from farm computers (lxpub …). To do this, use the dcap protocol or the dccp copy utility.

Access is made through processes running on the dCache server

lxse-dc01.jinr.ru:22126