Smart Storage and Linux An EMC Perspective Ric Wheeler

Why Smart Storage?  Central control of critical data  One central resource to fail-over in disaster planning  Banks, trading floor, air lines want zero downtime  Smart storage is shared by all hosts & OS’es  Amortize the costs of high availability and disaster planning over all of your hosts  Use different OS’es for different jobs (UNIX for the web, IBM mainframes for data processing)  Zero-time “transfer” from host to host when both are connected  Enables cluster file systems

Data Center Storage Systems  Change the way you think of storage  Shared Connectivity Model  “Magic” Disks  Scales to new capacity  Storage that runs for years at a time  Symmetrix case study  Symmetrix 8000 Architecture  Symmetrix Applications  Data center class operating systems

Traditional Model of Connectivity  Direct Connect  Disk attached directly to host  Private - OS controls access and provides security  Storage I/O traffic only Separate system used to support network I/O (networking, web browsing, NFS, etc)

Shared Models of Connectivity  VMS Cluster  Shared disk & partitions  Same OS on each node  Scales to dozens of nodes  IBM Mainframes  Shared disk & partitions  Same OS on each node  Handful of nodes  Network Disks  Shared disk/private partition  Same OS  Raw/block access via network  Handful of nodes

New Models of Connectivity  Every host in a data center could be connected to the same storage system  Heterogeneous OS & data format (CKD & FBA)  Management challenge: No central authority to provide access control Shared Storage IRIX DGUX FreeBSD MVS VMS Linux Solaris HPUX NT

Magic Disks  Instant copy  Devices, files or data bases  Remote data mirroring  Metropolitan area  100’s of kilometers  1000’s of virtual disks  Dynamic load balancing  Behind the scenes backup  No host involved

Scalable Storage Systems  Current systems support  10’s of terabytes  Dozens of SCSI, fibre channel, ESCON channels per host  Highly available (years of run time)  Online code upgrades  Potentially 100’s of hosts connected to the same device  Support for chaining storage boxes together locally or remotely

Symmetrix Architecture  32 PowerPC 750’s based “directors”  Up to 32 GB of central “cache” for user data  Support for SCSI, Fibre channel, Escon, …  384 drives (over 28 TB with 73 GB units)

Linux Wish List: Lots of Devices  Customers can uses hundreds of targets and LUN’s (logical volumes)  128 SCSI devices per system is too few  Better naming system to track lots of disks  Persistence for “not ready” devices in the name space would help some of our features  devfs solves some of this  Rational naming scheme  Potential for tons of disk devices (need SCSI driver work as well)