Storage Procurements Some random thoughts on getting the storage you need Martin Bly Tier1 Fabric Manager

20 June 2008 Stoarge Procurements - RAL You want How Much? Know your units –TB (10^12) is not the same as TiB (2^40) –Storage vendors talk in terms of TB and raw capacity –Define what you mean by 1TB and what you mean by your capacity requirements For the Tier1 procurements: –Capacity in units of 1TB=10^12 bytes –Usable capacity described in terms of RAID5 or RAID6 redundancy (or even RAID 1+0) –Thus N data drives will give (N-2)*Size_of_drives usable storage (R5,6)

20 June 2008 Stoarge Procurements - RAL Storage type Lots of sorts –SAN, NAS, DAS, iSCSI… Different technologies –FC, SCSI, SAS, SATA Arrangement –RAID levels, array/server arrangements Each appropriate for different use cases –Speed, cache/buffer sizes (disk, controller), battery backup units

20 June 2008 Stoarge Procurements - RAL Technical specs Specify what *you* want –In as much detail as is necessary to get it –Be as unambiguous as possible Three types of specification: –Mandatory – non-compliant if not provided –Desirable – youd like it but omission is not a non-compliance –Optional – gives the vendor some scope for added value Specify *everything* –Including CPU performance, RAM, NICs, which OS, acceptance tests, documentation requirements, maintenance and warranty etc Provide required (achievable!) performance metrics –And a recipe to do the tests… Define bid evaluation criteria before issuing the spec or call for tender

20 June 2008 Stoarge Procurements - RAL Technology issues Motherboard SATA controllers, NICs Issues with concurrent i/o performance of 3ware cards Are the drivers required for the components you need available in the version of the OS you intend to run –If not – are you prepared to build extra modules for them, and do it every time a new kernel comes along until it *is* available in the stock builds: c.f. areca driver in SL 4.6, kernel >= And you may have to add them to the installation kernel…

20 June 2008 Stoarge Procurements - RAL Technology Issues II In RAID systems, number of drives per controller: –Fewer drives, fewer concurrent drives used for read or write, lower performance –More drives, better performance, but performance drops off across the Span –Large RAID sets on single controllers are not recommended, though more than one RAID per controller seems OK

20 June 2008 Stoarge Procurements - RAL Technology Issues III Capacity per box –I/O bandwidth to disks –I/O bandwidth to network Memory – is more better CPU architecture OS issues Resilience Reliability

20 June 2008 Stoarge Procurements - RAL Large Procurements Where value large => EU tender rules Avoid specifications that mention Tradenames, OEM names, non- benchmarked performance indicators, proprietary technologies… –Unless referring to a common name for a part to a recognised industry standard commando plugs are IEC.309 / BS EN –But quote the standard first Use ISO, EN or BS standards –ISO and EN take precedence over BS where there is an equivalent EN. Some EN standards adopted as the BS. Be prepared for a long process –Restricted: longer, two stages, get to restrict the final bidders –Open: shorted, many more bidders to evaluate Can use Catalyst (GCAT) or other schemes For small volumes, exercise your supplier contacts

20 June 2008 Stoarge Procurements - RAL Random thoughts Weight, cooling, power consumption, power feeds, power redundancy, NIC redundancy, switch uplink capacity, warranty, availability of spares after maintenance period, Castor/dCache/DPM/xrootd, disks/controller, controllers/chassis, RAM per chip/core, chips/cores per chassis, redundant system drives, lights-out operation, component quality, interoperability with existing systems, chunk size