Raising the roof on the shingled write problem

Shingled writing has a serious problem: writes take more time than current disk writes, probably ruling out enterprise use unless complex flash memory technology is used. The problem stems from the layout of heavily overlapped tracks in shingled write recording (SWR) and the direction of writes. Together they mean that a …

[Anton Ivanov]

It should not be such a problem

The difference between a disk and a flash is that a disk can contain non-shingled and shingled areas which can be read and written by the same head.

If the physical writes are optimised to the current free shingled location and the journal is written to a non-shingled area a shingled disk can fly.

This concept can be taken even further. All writes can take place to a non-shingled buffer and moved to a shingled area in the background once the disk is idle. Allocating let's say 8G non-shingled write buffer on a 8TB drive is no big deal and there are very few applications which will produce more than 8G of data at a speed which is capable of saturating a drive.

This may even be done dynamically as needed and when needed.

[gratou]

SSD + shingled?

How about the buffer is SSD? The best of both worlds: fast SSD speed, large shingled capacity.

[Anonymous Coward]

If scientific research...

...and R&D was properly funded, you wouldn't have to pay for those papers. I pay a lot for my IEEE membership, and a considerable amount is free to the public. Premium research carries a premium cost, which has to be recouped from somewhere.

[Steven Knox]

Shurely...

the patent royalties will more than cover the cost of such research? These researchers did get patents on this, yes? Isn't that the entire point of patents?

[Matthew Glubb]

Unfortunate Terminology

Anything with shingles should be avoided.

[Daniel von Asmuth]

The need for speed

Before too long we are about to witness terabyte-sized hard-disc drives, which would take forever to copy. The focus should be on read/write speed and latency, not capacity.

[foxyshadis]

I think you missed the boat

I've already filled up a 2TB drive and two 1TB drives at home, and at the office, we have a brand spanking new SAN with 10 1TB drives (and 20 300GB) that are rapidly being filled up from all of the clunky old SANs.

A 2TB drive takes about 30-40 hours to format or copy.

[MadonnaC]

only 4 writes?

I would hazard more than that, as when you write subsequent tracks, surely you are overwriting even more of already laid down data. This would seem to imply that on average 1/2 the number of tracks would have to be rewritten.

[gratou]

shingled slow-write very useful..

>will enterprises buy shingled HDDs if rewriting data takes seven or eight times longer than with today's drives? Of course they won't. SWR drives won't find a place in applications where fast write I/O is a requirement.

Bad generalisation. It is the re-write that is slow, not the write. Back-up and archive disks can benefit from this technology right now. I reckon we'll see more and more specialised disks: expensive and fast SSD for OLTP (fast access time), cheap and slower SSD for 24/7 low-load servers (no wear, no heat), shingled for one-off writes (huge capacity, fast first write), etc.

Marketers will love this.