Talk:Linear Tape-Open

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[edit] Capacity figures

All capacity figures are assumed to be native capacity, uncompressed. It doesn't make sense to compare compressed figures. What is really getting stored on tape is just plain data. Just because it is the output of a compression algorithm, doesn't mean anything. Compressed figures have no place in the stat sheet. So we have no need to say redundant things like "Native Uncompressed Capacity." The statement is redundant.

Yes, I hate compressed figures. Yes, this is a rant. Yes, I care. Austin Murphy 19:24, 24 July 2006 (UTC)


[edit] Colours

Are the colours actually part of the standard or just the colours used by a particular manufacturer? All the HP brand 400GB LTO media I have seen was coloured dark red, which doesn't match the table in the article. --James 03:37, 18 October 2005 (UTC)


I have used HP LTO-1 (100GB/200GB) tapes, they're coloured blue.

All the LTO-2 cartridges that I have seen have been purple. I've seen Fuji, Maxell, TDK, HP, and Overland.

My cleaning cartridges are Black and are universal (across HP LTO-1 and LTO-2 drives at least).

[edit] WORM

Q: What does write-once, read-many mean in this context? Are the non-WORM varieties of tape only readable once? Or is it possible to write to them more than once?

A: It means you can write to the tape once, read it as often as you like, BUT you can't erase the tape or overwrite it. The idea is to keep some data indefinitely to meet regulatory requirements or for some other purpose. The regular varities of tape can be written and read until they wear out.

[edit] Recording characteristics

I've been googling this and the main page here is about all the info I can find!

Some of the questions I would have are:

What's the logical inter block gap (eg DDS is 4bytes, QIC is more like 2kbytes

Q: How does it react to already compressed data? (again DDS eg: logical capacity drops to about 60% if you don't physicall turn off the compression!)

A: The compression spec is aware of the possiblity that the data might already be compressed. If the compression ratio is less than 1 it turns off compression.


Q: I have found a couple of hits that the streaming requirements are easier than other tape drives, do the tape drives run at multiple speeds?

A: The HP LTO-2 Drive I use can stream at 10MB/sec to 30MB/sec. Other drives have different streaming ranges.


Later... Okay, I've put the stuff I did find eventually in the article looks like chop. chop time. 86.16.135.53 08:22, 26 March 2006 (UTC)

[edit] Units used for capacity and transfer speeds

Prefixes for bit and byte
Decimal
Value SI
10001 k kilo-
10002 M mega-
10003 G giga-
10004 T tera-
10005 P peta-
10006 E exa-
10007 Z zetta-
10008 Y yotta-
Binary
Value IEC JEDEC
10241 Ki kibi- K kilo-
10242 Mi mebi- M mega-
10243 Gi gibi- G giga-
10244 Ti tebi-
10245 Pi pebi-
10246 Ei exbi-
10247 Zi zebi-
10248 Yi yobi-

As the pages for binary units, gigabyte, etc. makes very clear, there is more than one interpretation for "GB". I'm not trying to start YAUW (Yet Another Unit War) but I do think we have to either:

  • Use MiB/s and GiB as these units aren't ambiguous

or:

  • Add an explanation (perhaps in the notes section) stating that the units for this page is 2^x or 1024^y

Doldr 16:05, 6 September 2006 (UTC)


That (the addition of the unit defs) made sure that people know what we mean. Now we just have to figure out which is correct for LTO... Information about this isn't exactly easy to find (maybe someone is sitting on detailed info?). The few clues I've found seem to indicate that (like hard drives and DVDs) LTO uses 10^9, not 2^30. This is what I've found:

-- Doldr 15:32, 7 September 2006 (UTC)


Not finding any conclusive information about this I turned to "experiments". With compression off I let dd fill up two different tapes (using one of our IBM LTO3 drives). Here are the results:

  • HP LTO2 tape: 212149993472 Bytes (197.6 GiB or 212.1 GB)
  • IBM LTO3 tape: 423524040704 Bytes (394.4 GiB or 423.5 GB)

My conclusion, LTO tapes as hard drives and DVDs are spec'ed in GB (10^9). In reality tapes are manufactured to be atleast that capacity (with some margin it seems). -- Doldr 12:19, 8 September 2006 (UTC)

Interesting experiment. What was the block size for dd? It appears that neither unit system precisely describes the capacity in round numbers. 200 GB == 186 GiB, and 200 GiB == 214 GB; double that for LTO-3. Is it possible that there are error sections that are unused? I wonder if the streaming speed had anything to do with it. -- Austin Murphy 18:13, 8 September 2006 (UTC)

The template of byte quantities is pretty cool. maybe we can use it. -- Austin Murphy 18:34, 8 September 2006 (UTC)

I used 1 MiB blocksize with dd and the streaming speed was close to peak (76 MiB/s for the LTO3 and a bit under half that for LTO2). I think we should try to "get to the spec", maybe ask IBM or lto.org in some way. Doldr 09:51, 11 September 2006 (UTC)


Check out this page: ECMA 319, it looks like 100 Gbytes, the units used in the docs, means 100 x 109 bytes. -- Austin Murphy 21:17, 23 September 2006 (UTC)

[edit] Backward Compatibility

The table in the "Generations" section currently lists LTO-4 as reading only LTO-3 and LTO-4 tapes, and writing only LTO-4. This would seem to conflict with the LTO Consortium's published information, which says that any LTO drive is required to read tapes of its own generation and at least the two preceding it (so LTO-2, -3 and -4 for LTO-4 drives), and write to tapes of its own and at least the immediate preceding generation (so both LTO-3 and LTO-4 tapes for LTO-4 drives). I realise that LTO-4 has yet to be finalised, but is there any reason to expect that the prior policy on backward compatibility will change? -- 210.54.3.3 07:13, 22 November 2006 (UTC)

I would prefer to delete those two rows from the table since they describe something other than that specific generation of LTO in that column. The rows ("Reading" and "Writing") describe interoperability between generations and do a poor job of it. The previous section describes it suitably anyway. -- Austin Murphy 22:27, 26 November 2006 (UTC)
I deleted those rows. -- Austin Murphy 15:28, 27 November 2006 (UTC)

[edit] Tape wear

Am I reading this article correctly w/respect to the number of passes over the tape required to fill a tape to capacity? It sounds as if an LTO-1 drive requires 48 end-to-end passes, while an LTO-2 drive requires 64 passes. What are the implications to tape wear and head wear? How does this compare to helical-scan tape formats? -- dpotter 23:52, 5 February 2007 (UTC)

You are reading it correctly. X total tracks / Y tracks per pass (head elements) = Z total passes. 512/8=64. In this configuration the head is essentially fixed while in a helical scan configuration the head is rapidly rotating against the tape. A helical scan configuration will only make one pass over the tape. Both cause more tape wear than one with knowledge of audio tapes might expect. I don't know which causes more wear. As an aside, I've heard that older rented VHS tapes frequently have a loss of signal at certain particular points on the tape. This is due to the pause function keeping the spinning tape head at the same spot on the tape, slowly wearing away the magnetic coating. You don't get this with linear tape systems, because "pause" is not even possible. Shoe-shining is a problem with high-speed linear serpentine tapes. If a drive is shoe-shining, then it is effectively making many more passes than normal. -- Austin Murphy 19:13, 6 February 2007 (UTC)

[edit] HH (Half-height) drives

I feel half-height drives should be mentioned for LTO-2 & LTO-3 (and very soon LTO4). Perhaps only a short excerpt about how they operate at ~3/4 the data transfer rate of their full-height counterparts but take up only half the size height-wise? Being that they still use the same media as they are named after, capacity of course does not change. -- halfmoon 01:48, 31 August 2007 (UTC)

[edit] Fair use rationale for Image:Lto-logo.png

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BetacommandBot (talk) 20:13, 2 January 2008 (UTC)