Robert/All
> Date: Thu, 17 Apr 2003 17:29:47 +0800
> From: Robert Loh <robert AT SOFTSOURCE.COM DOT SG>
> Subject: Re: Tape choices
> I think everybody is quite confuse about drive and media, correct me
if I am wrong
> Quantum Native Speed Native Capacity
> SDLT320 16MB/sec 160GB
> SDLT640 32MB/sec 160GB will be released end of 2003
> Understanding that SDLT320 support backward compatibility of SDLT220
but no sure about SDLT640
>From what I understand SDLT220 will backwards read DLT1 (benchmark) with
the SDLT head, or DLT4000/7000/8000 if you have a model with the
additional head in.
SDLT320 will read and write SDLT220 formatted tapes at 11mb/sec, and
DLT1, DLT8000, DLT7000 and DLT4000, but only at half speed (3mb/sec,
4mb/sec, 3.5mb/sec and 1.5mb/sec respectively). SDLT220 and 320 both use
the SDLT1 media type, although for full speed (16mb/sec) on SDLT320 from
a cartridge used in a SDLT220, I think you have to re-format? Else you
get 11mb/sec?
The SDLT600 due later this year will have a new media type, will at
least read SDLT220/320 and will have a native capacity of 300GB and
write at 32mb/sec. Details as far as I am aware are not confirmed yet
for this unit though?
> LTO1 15MB/sec 100GB
> LTO2 30MB/sec 100GB
> Don't think LTO2 is backward compatible with LTO1
Those figures relate to the HP or Seagate unit. The IBM units are rated
at 16mb/sec for LTO1, and 35mb.sec for LTO2, as someone else pointed
out. The LTO1 units from HP/Seagate have rate adaptation (will slow the
drive down if the incoming stream cannot keep up), the IBM unit does
not. All the LTO2 drives I believe have rate adaptation built in, so for
example the IBM unit can run at 17.5, 21.9, 26.25, 30.63, and 35 MB/s to
try and match a slow incoming stream speed.
LTO1 and LTO2 have different cartridges, although there is backwards
compatibility. LTO2 drives will backwards read/write LTO1 cartridges,
at LTO1 capacities, although sometimes faster, so for example the LTO2
drive from IBM will read/write an LTO1 cartridge at 20mb/sec, which is
faster than the 16mb/sec of the LTO1 drive it was designed for.
> Media is not depend on the drive, for example if we are using Media
with 160GB native, the only
> different is whether we are using SDLT320 or SDLT640 drive writting to
the media, the media capacity
> still the same, only the speed of writing to media is different.
This seems to be the case for SDLT and LTO at the moment, the LTO
consortium are committed to backwards read and write, although Seagate
seem to be hinting that the next generations may be read only, not sure
if anyone else has seen this?
One this is for sure, they are going to have to change the types and
possibly the format of the cartridges to achieve the next hike in
capacity and speed, 300GB for SDLT600, 400GB for LTO3 is a big capacity
for a tape!
And as Jose pointed out Sony are launching SAIT soon with its 0.5TB
native capacity and 30mb/sec it is certainly going to give people with
floorspace issues something to think about! Being Helical Scan as oppose
to a Serpentine technology, it should also give reasonable mount times.
> As what u see, SDLT and LTO are in the race to each other. Personally
I am quite happy working with
> SDLT320. Cheers... Robert
I think the problem is going to be, that no matter what you invest in in
terms of Technology you have to hook it up to systems that can run it!
LTO2 from IBM for example is 35mb/sec native, and at 2:1 compression
that would be a whopping 70mb/sec of data to get to a drive, and with
NetWorker that's a lot of streams if all you have is simple clients with
local disk!
Paul.
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