🚀 go-pugleaf

randy@psg.com (Randy Bush) writes:

>vhs@rhein-main.de (Volker Herminghaus-Shirai) writes:

>> I need to design a retrieval system for ~15TB of data, of which ~5TB are
>> retrieved with a high frequency (25 requests/second) and an access time
>> of avg. 30 seconds (max. 120 seconds). Retrieval lacks any locality, so the
>> 5TB are real random-access. The rest of the data is still accessed at a
>> rate of 5 requests/second.

>Optical RW store, a la HP.

He's talking *Tera*byte, not Gigabyte. The largest hp jukebox accomodates
roughly 100 GB. This project would require 150 jukeboxes for capacity
alone. But having 5 TB on MO disks in online access would mean no less
than 16000 drives! Assuming an MTBF of 20000 hours (data is for Sony
SMO-E501) means that you have to replace a drive almost every hour!

BTW, I believe the Subject: is somewhat off the mark. For a capacity
in the TB range, 25 requests/second requires extremely fast devices
(i.e. compared to jukeboxes taking a few second to exchange media).
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