The Escalade 6400...
Although Promise commands the majority of the ATA RAID market, several other companies realize the industry's potential. 3ware is such a company- in April of 1999, they introduced their first series of ATA RAID controllers: the DiskSwitch 4 series. Soon afterwards, 3ware introduced the Escalade 5000 series in 2, 4, and 8-channel configurations (model numbers 5200, 5400, and 5800, respectively). Contemporary ATA drives were rapidly approching the limit on ATA-33, outdating the 5000 series.
To remedy the situation, 3ware released the Escalade 6000 series last summer. Featuring the same 2, 4, and 8-channel options, the 6000 series differs mainly through its ATA-66 support. Like the SuperTrak, the Escalade series has a dedicated ATA channel for each drive; therefore, its ATA-66 interface should not be a limiting factor in the near future.
Escalade 6400 Specifications:
- 4 Ultra ATA/66 or Ultra ATA/33 drives;
- RAID levels 5, 0, 1, and 10;
- On-board processor reduces CPU overhead;
- TwinStor technology improves RAID 1 and RAID 10 beyond simple mirroring for redundancy. 3ware's advanced adaptive algorithms and drive profiling speed data access, yielding read performance that rivals RAID 0 striping for both large data files and smaller randomly distributed transactions;
- DiskSwitch architecture replaces the shared bus found in SCSI systems with a multiplexed data path that speeds data into system memory without burdening the host CPU;
- Greater than 100MB/sec sustained reads;
- Greater than 84MB/sec sustained writes;
- Stripe size selectable from 64K to 1MB;
- Elevator seeking, command queuing;
- Hot swap and hot spare capability;
- Windows 98, Windows NT 4.0, Windows 2000, and Linux (Red Hat 6.1, 6.2, SuSE 6.3, 6.4, TurboLinux 6.02 support. Driver available in Open Source Kernel 2.2.15 and beyond);
- 3-year warranty.
Like the SuperTrak 100, the Escalade 6400 is a full-length PCI card. It features four ATA connectors, two ATA-66 ASICs, and a dedicated RISC processor. The controller features four green LEDs - one next to each ATA connector. They individually light up whenever data is being transferred through each of their respective channels. These LEDs are a welcome feature to folks like us who always want to know as much as possible about what's going on with our hardware at any given time.
The Escalade includes the following items:
- Four single-connector, 80-conductor 18" ATA cables;
- 100+ page user manual;
- Driver disks and utility CD;
- Two Y-splitter cables to connect 2 drives to a single power supply connector.
RAID 5 support for the Escalade series?
On February 1st of this year, 3ware introduced a firmware upgrade that brings RAID 5 functionality to the Escalade 6400 and 6800 (not the 6200, of course, since RAID 5 requires at least three drives). Until this point, the Escalade had only supported RAID 0, 1, and 10.
How can a firmware upgrade enable a card to support RAID 5? There are two possibilities: 1) The card was always meant to support RAID 5 yet had it delayed by half a year or 2) The card was not meant to support RAID 5, but a decision was made sometime after the its release (perhaps due to the SuperTrak's RAID 5 support?) to implement RAID 5 at the firmware level. More on this later...
DiskSwitch and TwinStor: Quality engineering, or fancy marketing?
When one visits 3ware's website, it's virtually impossible to miss the words "DiskSwitch" and "TwinStor." These terms have been trademarked by 3ware, and refer to architectural features of their Escalade series of cards. Both terms are covered in great detail on 3ware's site, so we'll just present an overview here. Those seeking more detail may find the respective whitepapers here and here.
The term DiskSwitch actually comprises three aspects of the Escalade controllers: AccelerATA data channels, a packet switching controller, and the card's on-board RISC processor.
AccelerATA is 3ware's term for the dedicated ATA channel that each drive enjoys on an Escalade. These channels, along with the packet switching controller and on-board RISC processor, provide each ATA drive with full bandwidth to the host. 3ware claims to be the first company to use packet switching on a storage controller to both lower latency and provide exceptional scaling as more drives are added.
3ware's TwinStor architecture - used in RAID 1 and RAID 10 arrays - profiles each drive to allow for "maximum performance for the particular brand of drive used." TwinStor then maintains a statistical history of data accesses to allow sequential and random reads to be distinguished from one other. For random reads, TwinStor reorders I/O's and load balances them between all drives in the array; for sequential I/O's, TwinStor utilizes all drives in the array for maximum transfer rates. Since each drive in a RAID 1 or RAID 10 array has a mirror, proper load balancing of random I/O can provide performance which rivals RAID 0 arrays.
3ware's Escalade cards include a BIOS that allows arrays to be created or deleted. The BIOS also permits rebuilds and features a toggle for the write cache of an array. (note: Escalade cards do not feature onboard cache; the write cache referred to in BIOS is actually the buffer of the drives themselves). The BIOS also sports a verify feature similar to Promise's synchronization procedure.
Just like Promise's SuperCheck, 3ware's software utility, 3DM, allows arrays to be viewed, created, deleted, and maintained. Drives may be added, removed, or designated as hot spares. Also like the SuperCheck utility, 3DM can run in the background as a daemon and provide event notification functionality. The utility can either send an email or trigger a local event in Windows when an array becomes degraded or non-functional. In addition, the card's audible alarm may be toggled and the rebuild rate may be changed (faster rebuilding means lower system performance during rebuilds, and vice-versa).
The utility may be accessed via a web browser from any remote location as long as the two machines can connect to each other over a network. All of the utility's aforementioned features are accessible remotely - quite convenient.
A Note on Hot Swapping...
Though both cards claim hot swap capability, there's a difference between the two. As mentioned above, the SuperTrak Pro comes with three SuperSwap hot swap ATA drive enclosures. These enclosures allow drives to be inserted or removed without having to power down the machine. The Escalade, however, comes with no such enclosure, so a user wishing to take advantage of its hot swap support must purchase third-party hot swap drive enclosures.