iSCSI take-up has been hampered to a certain degree by a lack of serious support from blue-chip manufacturers but the news that Adaptec has joined the fray will be heartening news to many. However, even though the company has been busy recently acquiring companies such as Snap Appliances and Elipsan it doesn’t go for full immersion in iSCSI waters preferring to dip it toes in with a single storage product.
The Storage Array iSA1500 offers a good hardware specification that is essentially a complete Supermicro partnership of low profile SC813-T chassis and X5DPR-IG2+ motherboard which comes equipped with a single 1.6GHz Xeon processor and 1GB of memory.
Yet again we see SCSI getting its marching orders for network storage duties as the iSA1500 delivers a quartet of 250GB Maxtor Serial ATA (SATA) hard disks for a full 1TB of storage. It’s no surprise that many storage vendors are turning away from SCSI as although it has the edge on performance it can’t match the superb price/capacity ratio of SATA. It won’t be long before 300GB Ultra320 drives are available but we’ve heard that the price tag will be in the region of £800-£900 per unit which is just plain silly when you can get 400GB SATA drives for less than half this price. RAID is on the menu as you get an Adaptec 2410SA four-port PCI controller card with 64MB of cache memory and the drives are mounted in sturdy hot-swap carriers. The appliance is Linux-powered and this is implemented on a simple IDE flash memory card which runs Adaptec’s iSCSI target stack as well.
Installation starts with a brief visit to the CLI (command line interface) via a local serial port connection where a quick start wizard runs through basic network configuration. This does provide full access to the system but we found it much easier to use Adaptec’s Storage Manager Windows management utility. There’s still a fair bit of work to do as each system that is to access the appliance must have both the Microsoft iSCSI initiator and Adaptec’s agent service installed while Windows 2000 Server systems will also need Microsoft’s DiskPart utility loaded as well. Unsurprisingly, the agent also supports Adaptec’s 7211 HBAs but even with these installed you must still have Microsoft’s iSCSI service loaded.
It may seem tedious but the benefits are that Storage Manager can automate all iSCSI initiator portal configuration, target log on and drive assignments so you can decide which systems are allowed to access selected volumes on the appliance. Unfortunately, there’s still more work to do as the IP addresses of all systems running the initiator and agent must be entered manually. Adaptec did have an auto-discovery routine but advised us it removed it to avoid problems on larger networks.
From the well designed Storage Manager interface you can select individual appliances, create storage pools and implement RAID-0, -1, -10 or -5 arrays. Note that the Adaptec controller merely provides the SATA interfaces to the hard disks. All the hard work during configuration pays off now as the Automation feature allows you to select an agent and assign a disk volume and drive letter. No further work is required at the initiator end as the drive is automatically assigned to the chosen system where it appears as a local hard disk. Adaptec uses the concept of scopes allowing you to assign specific volumes to individual systems or groups of servers.
For performance testing we used the open-source Iometer running on a dual Xeon server. The iSA1500 delivered impressive results with two disk workers, 64KB request transfer sizes and 100 per cent read operations returning a speedy 91MB/sec. However, we have found in the past that the various iSCSI target implementations have different impacts on local processing for the systems running the initiator and for this test we saw processor utilisation at an above average fifty per cent. However, we reran the tests with an Adaptec 7211C HBA (reviewed here) installed in the same server and while raw throughput remained just as high we saw processor utilisation drop to a far more comfortable eight per cent.
The price also includes support for up to 64 volume snapshots so you can easily take point-in-time backups of selected volumes and schedule these to run at regular intervals. Backup options get even better as each snapshot appears as another iSCSI target so you could assign it to a server that has tape drives attached allowing you to implement backup for off-site storage at convenient times.
Despite the lengthy installation and configuration the iSA1500 does provide some useful iSCSI features and good assignment automation. It also delivers on storage capacity and performance making it a good choice for disk-to-disk backup and network storage in remote offices or smaller
The iSA1500 sits in the middle ground for iSCSI applications as it offers some IPSAN features normally found in enterprise level products but delivers them at a reasonable price. Installation is tedious but the automation and storage scope features more than make up for this and the price includes a useful snapshot backup feature