If you're looking for a simple and cheap way to set up a RAID array for important data, the Adaptec ASR 5445 serial RAID controller card could be for you. We found it easy to set up and fast to access data.
RAID (Redundant Arrays of Inexpensive/Independent Disks) comes in a variety of flavours — not all of which cater to redundancy. The type used depends on the specific needs of the individual storage system. Commonly, the purpose of RAID systems is to provide data security — there is always another copy of the information when something goes wrong. In some situations, such as Web-servers or high-end audio-visual systems — RAID can serve to balance the load on each drive thus ensuring better performance.
The simplest RAID types are 0 and 1. RAID 0 simply causes two or more physical drives to be seen as a single logical drive that expands storage space and improves performance by allowing simultaneous access to a single logical drive. RAID 1 mirrors physical drives so that the failure of one drive does not result in irretrievable data loss. When a replacement drive is installed the data is copied across with users being subjected only to lowered performance.
The Adaptec 5445 is a RAID 5 controller, and since it's a hardware solution the operating system is unaware of the existence of the RAID. Without getting bogged down in detail, RAID 5 allows for redundancy with less hardware than RAID 1 would require. For example, RAID 1 effectively stores only 100GB of data on two 100GB drives (half the space is used by the redundancy system). Using RAID 5, we can store 200GB on three 100GB drives (where one-third of the space is lost) or we can store 300GB on four 100GB drives (where one-quarter of the space is lost).
This greater efficiency is achieved by some clever, but simple, mathematics which uses a parity bit to allow reconstruction of any lost data. RAID 5 can only handle the failure of a single drive, two will cause data loss. RAID 6 can handle two failed drives so this might be something you will want to consider in mission critical situations where drive replacement cannot be quickly achieved.
Simplicity and reliability are our primary concerns with RAID systems. Therefore, we concentrated on the usability aspects of the device. We initially set up the device with two disks in RAID 1 (mirrored) configuration and then attempted to upgrade to RAID 5 (striped) after adding a third hard drive. We also assess whether this can be done and how easy it is to do. In other words, do you have to be an IT guru to succeed?
Speed is also important, but there is little reason why drive read/write speed should be seriously affected by incorporating a RAID system. Indeed speeds may even be higher due to the distribution of the data. We did a simple speed test on RAID and independent drives. This test involved combining two 760MB files and writing them back to the same drive. Timestamps from the output files were used to determine the drive speed, and the tests were run on a PC with a dual-core processor. We also timed the copying of a large directory (7.45GB) containing thousands of files and sub-directories.
Design and features
The card fits in a PCI Express (PCIe x8) slot and can be connected to either an internal or external drive array. To suit both standard and slimline cases, the card is supplied with internal cabling and faceplates. The faceplate is perforated to improve ventilation across the processor's heat-sink.
RAID configurations are numerous and may consist of various combinations of the types discussed above with variation for greater data storage reliability and or speed. The 5445 can handle RAID 0, 1, 1E, 5, 5EE, 10, 50 and 60, where 10 is a combination of 1 and 0, etc. The Adaptec Web site contains extensive descriptions of each array type and the relative benefits and disadvantages of each. The Adaptec device also allows for hot swapping of failed drives, where the RAID type supports such manoeuvres.
The card has its own 1.2GHz dual-core processor and 512MB of RAM enabling it to handle up to a huge 256 linked drives via SAS expanders. Up to eight SAS or SATA drives can be driven direct — four via external port and four internally.
The basic RAID management process is controlled via a BOS-based interface accessible on machine start-up. The utility allows arrays to be created and dismantled; boot settings can be adjusted and hot-swap drives can be prepared.
Adaptec Storage Manager software, which is supplied with the card, allows for more advanced management via a Web-based interface. Being Web-based means that all your Adaptec RAID cards can be managed from a single point. We didn't find the help interface particularly easy to use, and the help files were sketchy. This software is available for Windows, Solaris Linux systems, but not FreeBSD (which is certainly supported at BIOS level).
Setting up a RAID system is no drama. The supplied Quick Start Guide leads you through the basic menus using a bootable RAID 5 array as an example. We were able to quickly set up a RAID 1 array with two drives and were surprised to note that the information we had on the drives was retained after this process. Formatting of the drives would have been required if they had been previously used in a different RAID.
Sadly, we were unable to find a way to upgrade from RAID 1 to 5 so we created the RAID 5 array from scratch — no data on the disks were retained during this process. Worryingly, we had a bad time trying to convert the RAID 5 array back to standard disks.
Our copy test showed an impressive performance improvement for hard drives in both RAID 1 and RAID 5 configurations. Copy speeds for RAID 1 and 5 were improved by 50 percent and 60 percent respectively — these improvements are due to parallelism in read procedures. Although, these results could be a little lower when used with a single core PC.
The card comes with an excellent three-year warranty, and the Adaptec Web site has a variety of documents pertaining to RAID theory as well as user manuals. Users can also send queries to Adaptec online. However, the help files for the Storage Manager software need improvement.