Review: Toshiba AL14SXB90EN
Reviewed by: J.Reynolds
Provided by: Toshiba
Firmware version: 0101
Welcome to Myce’s review of the Toshiba AL14SXB90EN 900GB SAS 2 Enterprise HDD (hereafter referred to as the AL14SXB).
I have reviewed one of Toshiba’s 15,000 RPM, 2.5inch form factor, HDDs before, the Toshiba AL13SXB600N, which used a SAS 2 6Gbit/s interface (you can see this review by clicking here). The new AL14SXB90EN uses a SAS 3, 12 Gbit/s interface so it’s going to be interesting to see how they compare – please read on to learn what we find.
Market Positioning and Specification
This is how Toshiba positions the AL14SXB series of HDDs –
Here is Toshiba’s specification for the AL14SXB series –
Here are some pictures of the AL14SXB90EN I tested –
As is typical for Toshiba drives it is solid and well built.
Here’s a quick recap of the advantages offered by the SAS Standard.SAS utilises the Small Computer Systems Interface (‘SCSI’), which is a set of standards including a functionally rich and proven command set, for the physical connection and transfer of data between computers.
There are three types of SAS devices:
Initiators include Host Bus Adapters (‘HBAs’) and Controllers. They are the point at which an IO operation is initiated and sent to a Target Device. Initiators are located in Host Computers/Servers. An initiator allows the attachment of one or more Target Devices and Expanders to form an ‘SAS Domain’
2. Target Devices
Target Devices include SAS devices, such as SAS HDDs, SAS SSDs, and SAS Tape Drives. An SATA HDD or SSD can also be attached as a Target Device.
Expanders are low cost, high speed switches, which allow the number of target devices attached to an SAS Domain to be increased.
It is worth noting that an SATA drive can be attached as a Target in an SAS domain; however, an SAS device cannot be attached to an SATA controller. SAS and SATA Target Device connectors are physically very similar, but a ridge between the data and power connectors stops an SAS target connector being plugged into an SATA device.
Target Devices are attached to initiators through one or more SAS links. At the initiator, SAS links are typically arranged into groups of 4 (or 8), known as a wide port. Mini SAS 4 Link Cable Connectors are typically used to connect internal (‘in the host’) initiators to external (‘outside the host’) physical storage device containers/racks.
All SAS based storage drives have at least two ports, whilst SATA based devices only have one. SATA is a point to point solution and a device may only be attached to one port on an SATA controller or one SAS link in an SAS topology.
SAS supports ‘active cables’, which are thin cables with active circuitry to reduce cable weight and increase signal voltages. This allows SAS cable lengths to be up to 10m long, whereas SATA cable lengths are limited to 1m. Cable length is an important consideration when designing the physical implementation of an SAS multi-domain, high availability, topology.
SAS Target Devices can therefore be attached to more than one SAS domain (and therefore more than one Host), so that if one Domain (Host/Controller/HBA) fails it can still be accessed through another; this ability to design in fail safe measures is considered to be a significant advantage in Enterprise systems.
So, for example, an SAS based implementation could look like this, where the dual port capability of SAS drives is used to provide a high degree of protection against the failure of an initiator and/or it’s Host –
In this configuration an access path to each of the SAS SSD Target Devices can survive a failure of one of the Hosts/Servers, one of the Initiators/HBAs, one of the Expanders, one of the 4x wide port connector cables between Host and Expander, or indeed one of the individual SAS Links between Expander and Target Device.
The SAS standard continues to evolve and we can expect to see SAS 4 (24 Gbit/s) products arrive by 2019.
Now let’s head to the next page, to look at the Performance Tests conducted in this review…..