Friday, September 28, 2007

Multi-Tier Storage revisited

Its been a year since I posted here regarding Stanford's current and planned use of various storage solutions to virtually eliminate tape-based nightly archiving. Since then, the industry has gone through various changes, and in some cases, not much change at all.

Specifically, part of our solution used NeoPath's FileDirector for file based virtualization, and SBEI's iSCSI target solution for our backend storage. In the middle, pulling data from our primary NetApp fileservers, was a burgeoning solution being BETA tested at Stanford from Nexenta. So what has changed? NeoPath was acquired by Cisco, with the current product in production ceasing to be supported. SBEI has been acquired by NeoNode, and their iSCSI target, best in class for enabling commodity storage, isn't getting much love. How has Nexenta fared? While we will likely need to migrate away from the other solutions, the increasing capabilities of Nexenta's storage solution and its underlying OpenSolaris base have proceeded a pace, and I believe the future is very bright for this solution.

The NexentaStor product, in early BETA, delivers today on providing a snapshot based large scale file system, utilizing underlying storage pools (iSCSI, SCSI, SATA, FC, etc) and a well developed services architecture including data synchronization and replication, multi-host data tiering, and other facilities with data retention and disaster management to boot. Its base system disks even have bullet proof checkpointing, reversion, and safe updating, redundancy, all in a software solution. The future? Well, its easy to perceive with upcoming NFS v4.1 support that the product can tackle name space virtualization one has found in products such as the NeoPath. Already it can repurpose snapshot-based raw volumes as iSCSI targets, so if the underlying hardware is supported by OpenSolaris, you have an easily managed enterprise-feature level iSCSI target product.

Stanford has over a years worth of second tier data, in both 60 daily and 12 monthly snapshots, tiered from our NetApp. These are within many separate folders, representing over a thousand snapshots per volume. We've recently adopted the Sun X4500 24TB product and have migrated to this ideal solution for quicker disaster recovery. The read speeds on this 48 drive unit are great, and the price point rivals what we've built with iSCSI. Commodity storage is commodity storage, but we continue to utilize iSCSI, DAS (SATA-to-SCSI units), and other additional units to eclipse 48TBs of secondary storage. We have also utilized this solution for one organization as both first and second tier storage, an additional 16TB when we consider their solution, and it has proven its worth both in day to day NAS use as well as some data recovery and full disaster recovery modes.

Now that Nexenta supports some backup software as well as a client, we've only backed up directly to tape from the second tier once per year. We've let our LTO-2 tape library run continuously for around a week just to give us a full archived edition of our data. Are we missing tape reuse, tape-based recovery, or multiple library scheduling (and rescheduling) just to meet an ever growing nightly backup window? Nope. Nexenta looks to be here to stay.

I'll follow up later with specific details on configuration, where I hope things will go, and other random thoughts. On this anniversary, it would appear commodity-based multi-tier storage is practical and readily available.