Which SRM

Which SRM?

If you're starting out, how will you know which SRM or disk pool manager to install?

As part of the strategy, the GridPP Storage Community endeavour to support all three commonly used SRMs: the DESY/FNAL DCache and the LCG DPM, along with StoRM. DPM and dCache provide disk pool management with an SRM interface, whilst StoRM provides an SRM "shim" in front of a dedicated storage solution (like Lustre or HDFS, for example).

• What's everyone else using?

Basic Summary

• dCache was built to support large sites with complicated needs.
• DPM was built to support smaller sites with simple needs.
• StoRM was built to support sites who already have dedicated pooled storage.

What is a small site?

According to LCG's documentation (July 2004) a small site satisfies all of the following:

• Provides 1-10TB of storage, usually system-attached to nodes.
  • Note that this is a measure that should be applied to your available storage now (or in July 2004) - in the LHC era even T2s will offer many 10s or 100s of TB. DPM has no intrinsic limit to the amount of disk it can manage.
• No SAN architecture.
• No grid enabled tape storage.
• No full-time support for storage solutions. Only a fraction of an FTE available to manage the system.

In particular, DPM was intended as a replacement for the "Classic SE".

How do I choose?

1. Decide whether you are a small site.
2. Decide whether you really really want to run dCache, or really really want to run DPM (as opposed to "I just need an SRM").
3. Browse through the documentation for your preferred option.
4. If in doubt, get in touch with us! Join the mailing list! Read the archives! Talk to others who are running one (see the site overview below).

See the Grid Storage page for details.

When you have chosen

The caveat is that we may not be able to support 20 new sites at the same time. So normally you and we would agree with GridPP deployment when it's your turn. But don't let that hold you back, we try to support everyone as best we can.

1. Join the mailing list.
2. Read the documentation and start installing one.
3. Ask for help if and when you need it.
4. Attend the EVO conferences.

See the Grid Storage page for details.

Site Overview

Currently most UK Tier-2 sites have DPM, with 2 using dCache, and 2 (and a bit) with StoRM.