HD16

Discuss the Zoom HD and R series. Please don't "post and run". Participate in the discussion. Thanks.
Klink
member in good standing
member in good standing
Posts: 30
Joined: Mon Jul 26, 2010 7:14 pm

Re: HD16

Post by Klink » Mon Jul 15, 2019 10:17 pm

Thanks Jim, but if you look in this thread people have had success (not everyone) with 128GB & even 160GB so I don't reckon that's the problem. It's all a bit hit & miss really as to whether this all works it seems.
0 x

Wulfraed
The Force
The Force
Posts: 3233
Joined: Wed Jan 23, 2008 8:18 pm
Location: Lowell, MI

Re: HD16

Post by Wulfraed » Tue Jul 16, 2019 11:12 am

Jim_Fogle wrote:
Mon Jul 15, 2019 7:00 pm
One problem you may not have thought of. SSDs do not like user to use the defrag command. Instead, Windows has the TRIM command. I don't know how that affects use over time.

Optimally, there should not be any justification to even do a defrag on flash memory media (of any type).

On a spinning disk, a good defrag algorithm does two things:
  • It moves parts of a file that are on different cylinders so they are on a single cylinder -- this means only one head seek is needed to read the contents, rather than having seek/settling delays
  • It linearizes the file contents so that it can read the entire contents with minimal rotational delay (depending upon the drive performance, this could mean interleaving data so it can read a sector, transfer it while skipping the next sector, and then read the third, etc.)


Flash memory media has neither of those concerns. There are no moving parts which require delays.

What flash memory media DOES have, however, is the concept of allocation blocks (which are larger than the OS logical sector/block operations). The OS may use a cluster size of, say, 4kB (8 512kB sectors) as the transfer unit. Allocation blocks may, in contrast, be multiple MB in size.

Where magnetic media can rewrite sectors freely, flash memory can not. Writes to flash memory can only change bits in one direction. This means to rewrite a file one needs to /erase/ the destination (often to all 1-bits) before one can write (changing 1-bits to 0-bits). Erasing is done by allocation block. The media obtains a free block from the unused pool, erases it, then writes the modified data to this block (and copies any unmodified data from the source allocation block), and finally puts the old source block into the free pool.

Good media can keep multiple allocation blocks in an "open state", so appending data doesn't force additional allocate/erase/copy cycles. Cheap media may only handle two open blocks (which would be the FAT and one data file -- on a device that can record 8 files in parallel, that makes for a lot of allocate/erase/copy cycles as updating each of the 8 files triggers a cycle). Granted, this will be seen most in cheap SD cards* -- an SSD should have much better block management.

You'll notice that this allocate/erase/copy operation will rapidly "fragment" flash memory media. Flash memory should also implement wear leveling, to avoid reusing (erasing) blocks too often, as each has a limited number of erase/write cycles. Running a defrag on flash media will just result in rapidly using up erase/write cycles on the entire media.




* This is why low-budget Class 10 SD cards may perform /worse/ than a higher-cost Class 4 card -- Class 10 is rated on the concept of streaming video onto a freshly erased/formatted card (ie; a single long file is being written); Class 2/4/6 is rated on writing smaller files onto a potentially fragmented card (ie; still photographs with some deletions). So a Class 10 that only has 2 open allocation blocks will bog down badly given multiple smaller files, while a "slow" Class 4 with 6+ open allocation blocks doesn't lose as much time doing the allocate/erase/copy stuff.
1 x
--
Baron Wulfraed
IISS Elusive Unicorn (detached)

Superscope PSD-300; BOSS BR-600, Zoom HD16cd, Zoom R16, BOSS BR-800, Zoom H2n
Now to (re)learn to play an instrument

Lanikai S-C, SMC-E; GoldTone Banjo-Uke; Flatiron 1C, A5; Big Muddy M1-W; Ovation MM68AX, CSE-44; Orpheus Valley Fiesta FS; Taylor NS-72ce, T5-S1; Musima (4st, 20 fret, tenor-tuned) banjo; bongos, dumbeks, bodhrans, hand drum, tambourine; recorder: soprano, alto, tenor; Cedar Flute (5 sizes); Pennywhistle (3 keys); Casio keyboards

Post Reply

Who is online

Users browsing this forum: No registered users and 3 guests