Reply To: Multitrack recording skipping

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Nicola A&H
Keymaster

Hi all,

Where to start.

Yes the buffer size is a key factor in preventing dropouts in the write process, as it compensates for the difference between the rate at which data is transmitted and the rate at which it can be written on the drive. When a USB storage device causes a pause that is longer than the buffer time, a dropout occurs and data is lost. Qu-Drive has a limited buffer when compared to a computer, but as some of you have noticed, one of the V1.4 improvements to Qu-Drive was allocating some extra memory for buffering.

As we cannot reproduce the dropouts with any of our recommended drives, freshly formatted and V1.4 running on the mixer, we can only assume most of the issues reported here are due to mechanical conditions such as vibration. Robbocurry and others have posted about this, and this is what I found on an HGST tech sheet (look at the test results of a hard drive on a shaker in their article!):

One of the greatest hindrances to hard disk performance is vibration. Like a needle on a record, the disk drive’s head must try to follow narrow data tracks in order to read (or write) information. Physical disturbances can throw the head off-track and cause a delay while the actuator repositions it. This eventually has an impact on the hard drive’s input/output performance.

You are also correct in thinking that SSD and flash thumb drives are virtually immune to this problem. However, SSD drives can be prone to other issues such as performance degradation over time as DMAudio has pointed out. As for USB keys, most aren’t fast enough for multitrack recording, hence our reluctance in recommending this medium. Qu-Drive requires a continuous data rate of around 21 Mbit/s when recording multitrack. Unfortunately manufacturers of USB keys typically publish burst (max) write transfer rates, which are of little significance here. Sustained rates are seldom published.

We had good reports of Sandisk Extreme USB keys (available in 16, 32 and 64 GB) and must say this is looking promising here. We need some further testing but we definitely want to include some of these devices in our list of recommended peripherals. However please be aware that another problem common to both SSD and USB keys is the batch variance of memory chipsets used by manufacturers – a device might perform well in our tests, but the same model purchased in the US or six months down the line could show different performance. I guess this is the reason why other pro audio manufacturers have been much vaguer with their recommendations.

Ultimately our list should be taken as a guideline only and you should always test the USB device thoroughly before putting into service.

Hope this helps.