Elegance in storage from OCZ.
The Z-Drive boasts a storage capacity of 256GB at a gigantic price of $1750, which those clever ones out there will have noticed is exactly four multiples of a single 64GB SSD. In actual fact this is both perceptive and correct - the image below shows what is essentially four independent drives mounted onto two pieces of PCB. The individual chips that OCZ has chosen to use are Toshiba TH58NVG5D1DTG20, which is an otherwise incomprehensible string of characters. Delving back into the dark world of mathematics again (gasp) gives us four rows at four deep of flash chips that are 4GB in size, giving us an easy 64GB.
Performance-wise these MLC chips do hinder the Z-Drive somewhat, though in a comparison with individual flash chips (online here) we can see that the Toshiba chips used have decent 19.2MB/s reads, 12.9MB/s sequential write and 4.6MB/s random write - used together, all sixteen chips will provide the performance for the whole drive, and each four drives add up to a whole mess of performance.
This is arguably the most elegant SSD-based storage solution we've ever seen. The four individual 64GB SSDs, installed on two large PCBs, simply slot into the large metal cover as seen in the product shot. Data connectivity is provided internally via a dual-sided SAS connector that doubles up with power, though the card does need an external Molex cable for additional power.
The main PCB of the Z-Drive, the green one pictured, is where the interface between hardware and software begins. Sporting a RAID controller, specifically the LSI Logic LSISAS1068E, this grants hardware RAID 0/1 capabilities for stripe arrays and mirrored arrays. The former gives access to the entire 256GB capacity of the four drives, while the latter sacrifices half the storage space for a redundant copy of the data. Bandwidth for the card is immense - eight PCIe lanes give up to 4000MB/s theoretical maximum transfer rates, so the interface is definitely not going to be a bottleneck.
However, not all is rosy in storagetown. We installed the Z-Drive into our X58-based testbed, and gave it a run through with HDTach - returning typical access speeds of 0.1ms, but a poor read speed of 127.8MB/s. Burst read speeds were more impressive at 394MB/s, shining light on the fact that perhaps HDTach isn't the best method of testing such a zany high-end product. We fired up IOMeter to see if performance was significantly better, and the results were much more consistent with the rating of the flash chips.
When reading files, we got random access transfers of roughly 10,000 IOPs, which isn't a significant increase over a standard hard drive. Random writes were also quite slow, and it was clear that juggling small writes over four drives was not the best use for this card. Transferring a large single file to the Z-Drive was phenomenal however; writing a single large 2GB HD video file from our Intel 80GB SSD at over 200MB/s, and reading a single large file from the drive gave us an easy 420MB/s sustained.
What this ultimately means for the Z-Drive is that it isn't the smartest choice as a system drive; not because performance is lacking (which it isn't), but because it simply doesn't compete in price to a single SSD. It's not a smart choice as a storage drive either, and you'd have to be insane to grab one of these for backing up files. Where this drive becomes a viable choice is for those editing gigantic video files, 5.1 audio with multiple sources at once, or those working with gigantic databases. So while Z-Drive fails to live up to the excitement that it sparked, it's definitely something that is worth coveting.
Issue: 137 | June, 2012