Edit: Still good information.
Originally posted April 17, 2012 on AIXchange
In case you’re wondering why this server blog just published a post about storage, it’s simple: Without storage, servers don’t have anywhere to read and write their data. Many of us server admins do have some knowledge of storage, but many more do not. Understanding the differences between storage technologies is important. It can help us when we need to discuss our options with our storage friends.
Anyway, back to Norman Bogard’s storage webinar. By the way, although I wish everyone had access to this training, it was provided exclusively for IBMers and IBM Business Partners. The content is not available online, which is why I’m posting this information (with Norman’s permission).
I’ll continue with a rough summary of how he compares and contrasts network-attached storage and storage area networks. We’ll start with SANs:
“Block-level storage devices and SANs like IBM V7000, IBM DS8000 and IBM XIV provide access to equal sized blocks of storage, and the blocks are found by block numbers on a device. All read and write operations are performed on data blocks – mainly using the SCSI protocol. Block services are segmented into LUNs or vdisks, and you might usually have a few dozen of them.
“On the other hand, NAS devices like N series, SONAS or V7000 Unified provide access to files. These files are found by a name within a tree of names: read, write, create, delete and many more. CIFS, NFS, FTP and other protocols are used to access these files. Device services are exposed as exports, directories and files, and in this case we might be accessing a few hundred, or possibly even millions or billions of files.
“Your NAS may be connected to hundreds or thousands of client machines. Authorization is handled by user IDs for reads, writes and meta-data operations.
“Who owns the filesystem? With direct-attached storage, it’s a simple case. The storage lives on the server. Think of regular SCSI disks and expansion drawers filled with disks, or old SSA drawers of disks.
“With a SAN, the server still owns the files and it controls how the data is written to the disk, even though those disk arrays might be on a disk subsystem instead of internal disk. NAS, on the other hand, handles the filesystems and the files and just gives you access to them after you have authenticated.
“With converged, or unified, storage, there are two fundamental approaches to intermixing block and file storage within a single system. IBM’s N series uses block on file. A device file with a logical unit number (LUN) assigned to it is stored within the file server’s WAFL (write anywhere file layout) file system and then mapped to a host. File and block data are stored within the same file system.
“IBM’s Storwize V7000 Unified uses file on block instead of WAFL. A raw device from the V7000 is mapped to hosts. File data is contained within discrete devices. Host block data is contained within discrete devices. File and block data are stored independently.
“Based on your application type, rules of thumb can help you decide whether NAS or SAN makes more sense in your environment.
“Applications and data types that typically reside in block stores or SAN include RDBMS (Oracle, SQL Server, DB2), analytics (stream processing), OLTP, metadata layers (component of content management), e-mail (MS Exchange, Lotus Notes) and virtualization stacks (VMware: VDI, VMDK implementations, HyperV; Citrix Xen)
“Applications/data types that typically reside in files or NAS includes rich media (pictures, videos, seismic data, medical imaging, etc.), VOD, AOD, IPTV analytics (SAS grid), enterprise content management (ECM, e.g., web stores), research data sets, user files (documents, etc.), product lifecycle/data management (PLM/PDM) and virtualized environments (VMware client-driven deployment).
“Another consideration is how you backup these different environments. With NAS you typically have consistent snapshots since the files and filesystems are consistent on the NAS device. Replication is supported, and NAS usually integrates with backup software.
“With a SAN, integration with the host file system is needed to ensure consistency. Many times backups are moved through a master media server to disk or tape. Replication is supported once the file system is consistent.”
The webinar also covers file systems, file shares, network services, authentication and authorization, quota, data availability, data protection using snapshots, backups and replication, antivirus support and file cloning.
I love education in this format. This webinar takes a big concept like storage and breaks it down to easy to comprehend descriptions. We may work on servers, but servers connect to storage. That’s why learning about storage is worth our effort.