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Groups > comp.lang.forth > #14912
| From | anton@mips.complang.tuwien.ac.at (Anton Ertl) |
|---|---|
| Newsgroups | comp.lang.forth |
| Subject | Re: Implementing virtual memory on cassette tape |
| Date | 2012-08-10 15:57 +0000 |
| Organization | Institut fuer Computersprachen, Technische Universitaet Wien |
| Message-ID | <2012Aug10.175704@mips.complang.tuwien.ac.at> (permalink) |
| References | (3 earlier) <9438bee2-42d2-45a4-8d0c-a9e47baa2f80@j11g2000vbc.googlegroups.com> <2012Aug9.080022@mips.complang.tuwien.ac.at> <c5f1248a-11dd-4cca-b710-b95ea69d6c5f@y1g2000vbx.googlegroups.com> <2012Aug9.154425@mips.complang.tuwien.ac.at> <46bbc85d-2dab-40cd-a4a0-6e4550e969b5@i7g2000vbc.googlegroups.com> |
Alex McDonald <blog@rivadpm.com> writes:
>On Aug 9, 2:44=A0pm, an...@mips.complang.tuwien.ac.at (Anton Ertl)
>wrote:
>> Alex McDonald <b...@rivadpm.com> writes:
>> >On Aug 9, 7:00=3DA0am, an...@mips.complang.tuwien.ac.at (Anton Ertl)
>> >wrote:
>> >> Sounds like you swallowed some horror stories some people like to
>> >> spin. =3DA0Why should spin down exacerbate these problems?
>>
>> >Several reasons.
>>
>> >Rated start/stop cycles; 250 average on/off cycles per year at the
>> >expected population AFR of 0.55% (Seagate Cheetah 15.7, enterprise
>> >class drive).
>>
>> What does AFR have to do with the horror stories about corrupted data?
>
>AFR includes corrupted data.
It includes other failure modes, so this says nothing about spin-down
exacerbating disk corruption.
>> And anyone who uses "enterprise class" drives for backup has too much
>> money.
>
>Why? Since many operations value data integrity greater than the cost,
>this is an economic argument, not one of wealth causing stupidity.
In backup and also in RAIDs, we increase safety/reliability through
redundancy. For a given amount of money, we get more
safety/reliability by using more cheap drives instead of fewer
expensive drives.
>And AFR includes corrupted data. I'm mystified; where did I say that
>corrupted data was the only issue?
You spun horror stories about data corruption as if it was the main
issue. In my experience it's a minor issue.
>> >Drives vary; SATA drives at 5k RPM spin up faster than high RPM SAS
>> >drives at 15K, which may take minutes to stabilize at operating speed.
>> >During that time, the disk isn't usable, and I stand by my assertion
>> >that spin up wastes as much power as several minutes of full
>> >operation.
>>
>> Sure, if a drive takes several minutes to spin up, it will consume as
>> much power as several minutes of full operation.
>>
>> But who in his right mind uses an expensive and power-hungry high-RPM
>> drive that takes forever to spin up for a storage solution that
>> requires low power and fast spin-up? =A0Ok, a sales guy selling to a
>> clueless and rich customer will do it, but not because of technical
>> merit.
>
>I was giving an example of slow spin up to counterpoint the "10
>seconds and you're good to go" example you gave.
It's an irrelevant example, because nobody in his right mind will use
such drives for such a design. The 10s example is an ordinary 7200rpm
drive. If somebody wanted to use special drives for a spin-down
system and spin-up time is of any relevance, they will choose drives
that spin up at least as fast as the one I measured.
>To spin up a RAID group of say 14 drives on a shelf of disks will
>require that the drives are turned on serially in small groups.
No. If the hardware cannot spin them up at the same time, one will
not choose such a large RAID group. Conversely, if RAID groups of 14
disks are desired, the hardware should be designed so that the group
can be spun up at the same time. For a system that contains 480 disk
drives, dimensioning the power supply such that it can spin up 14
drives at once should be no problem.
>> >I don't know where you got the idea that 480 tape drives was the
>> >equivalent to 480 disk drives, but it's not an assertion I made and
>> >certainly qualifies as insane.
>>
>> You claimed that lots of disks had to be spun up for bandwidth
>>
>> reasons, and you wrote:
>>
>> |It's the economics of competing with tape; big power supplies to
>> |support 480 disks packed in a single rack cost lots of money.
>>
>> which suggest that you think that a backup solution needs 480 disks
>> spun up for bandwidth reasons.
>
>No, that was the COPAN solution. (IIRC it was the smallest COPAN
>system you could buy.)
And you claimed that their solution was insufficient because they
could only spin 25% of the disks, and that that was insufficient
because it limits the bandwidth too much.
>> It's nonsense, because we are backing up to disks with a total of 10s
>> of TB, and it's workable, and if we wanted to back up to more disks,
>> we would just use more disks. =A0And the main bandwidth limit is, as you
>> write, getting the data off the main storage.
>
>That was my point. If you want off-server backup, then the bandwidth
>off the server is the issue.
For our servers, the bandwidth off the server disks is the limit most
of the time, because there is a lot of seeking during backups, and
also, the data is already compressed when it goes off the server.
- anton
--
M. Anton Ertl http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
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Implementing virtual memory on cassette tape chitselb <chitselb@gmail.com> - 2012-08-07 06:21 -0700
Re: Implementing virtual memory on cassette tape Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-08-07 08:44 -0500
Re: Implementing virtual memory on cassette tape anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-08-07 14:01 +0000
Re: Implementing virtual memory on cassette tape Mark Wills <markrobertwills@yahoo.co.uk> - 2012-08-07 07:24 -0700
Re: Implementing virtual memory on cassette tape Stan Barr <plan.b@dsl.pipex.com> - 2012-08-07 15:30 +0000
Re: Implementing virtual memory on cassette tape Stan Barr <plan.b@dsl.pipex.com> - 2012-08-07 17:36 +0000
Re: Implementing virtual memory on cassette tape Jason Damisch <jasondamisch@yahoo.com> - 2012-08-07 11:52 -0700
Re: Implementing virtual memory on cassette tape Paul Rubin <no.email@nospam.invalid> - 2012-08-07 12:39 -0700
Re: Implementing virtual memory on cassette tape Paul Rubin <no.email@nospam.invalid> - 2012-08-07 12:55 -0700
Re: Implementing virtual memory on cassette tape Bernd Paysan <bernd.paysan@gmx.de> - 2012-08-07 22:00 +0200
Re: Implementing virtual memory on cassette tape Paul Rubin <no.email@nospam.invalid> - 2012-08-08 00:27 -0700
Re: Implementing virtual memory on cassette tape Mark Wills <markrobertwills@yahoo.co.uk> - 2012-08-08 01:26 -0700
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-08 02:31 -0700
Re: Implementing virtual memory on cassette tape Paul Rubin <no.email@nospam.invalid> - 2012-08-08 02:46 -0700
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-08 02:23 -0700
Re: Implementing virtual memory on cassette tape anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-08-08 10:57 +0000
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-08 04:59 -0700
Re: Implementing virtual memory on cassette tape anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-08-08 12:24 +0000
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-08 11:10 -0700
Re: Implementing virtual memory on cassette tape Bernd Paysan <bernd.paysan@gmx.de> - 2012-08-09 00:13 +0200
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-08 16:05 -0700
Re: Implementing virtual memory on cassette tape Paul Rubin <no.email@nospam.invalid> - 2012-08-08 17:30 -0700
Re: Implementing virtual memory on cassette tape Bernd Paysan <bernd.paysan@gmx.de> - 2012-08-09 03:26 +0200
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-09 05:30 -0700
Re: Implementing virtual memory on cassette tape Bernd Paysan <bernd.paysan@gmx.de> - 2012-08-09 19:21 +0200
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-09 13:30 -0700
Re: Implementing virtual memory on cassette tape Bernd Paysan <bernd.paysan@gmx.de> - 2012-08-10 01:27 +0200
Re: Implementing virtual memory on cassette tape vandys@vsta.org - 2012-08-09 00:32 +0000
Re: Implementing virtual memory on cassette tape Bernd Paysan <bernd.paysan@gmx.de> - 2012-08-09 03:33 +0200
Re: Implementing virtual memory on cassette tape anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-08-09 06:00 +0000
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-09 05:26 -0700
Re: Implementing virtual memory on cassette tape anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-08-09 13:44 +0000
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-09 10:21 -0700
Re: Implementing virtual memory on cassette tape Bernd Paysan <bernd.paysan@gmx.de> - 2012-08-09 19:50 +0200
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-09 12:32 -0700
Re: Implementing virtual memory on cassette tape Bernd Paysan <bernd.paysan@gmx.de> - 2012-08-09 22:07 +0200
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-09 13:58 -0700
Re: Implementing virtual memory on cassette tape Paul Rubin <no.email@nospam.invalid> - 2012-08-09 17:36 -0700
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-10 04:13 -0700
Re: Implementing virtual memory on cassette tape Paul Rubin <no.email@nospam.invalid> - 2012-08-11 20:27 -0700
Re: Implementing virtual memory on cassette tape anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-08-10 15:57 +0000
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-13 05:23 -0700
Re: Implementing virtual memory on cassette tape anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-08-15 15:13 +0000
Re: Implementing virtual memory on cassette tape Alex McDonald <blog@rivadpm.com> - 2012-08-15 11:57 -0700
Re: Implementing virtual memory on cassette tape anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-08-08 07:08 +0000
Re: Implementing virtual memory on cassette tape chitselb <chitselb@gmail.com> - 2012-08-08 06:25 -0700
Re: Implementing virtual memory on cassette tape Mark Wills <markrobertwills@yahoo.co.uk> - 2012-08-08 01:23 -0700
Re: Implementing virtual memory on cassette tape kenney@cix.compulink.co.uk - 2012-08-08 05:06 -0500
Re: Implementing virtual memory on cassette tape Percy <percival.andrews@gmail.com> - 2012-08-08 21:11 -0700
Re: Implementing virtual memory on cassette tape chitselb <chitselb@gmail.com> - 2012-08-08 21:30 -0700
Re: Implementing virtual memory on cassette tape percival.andrews@gmail.com - 2012-08-08 23:50 -0700
Re: Implementing virtual memory on cassette tape chitselb <chitselb@gmail.com> - 2012-08-09 03:54 -0700
Re: Implementing virtual memory on cassette tape Paul Rubin <no.email@nospam.invalid> - 2012-08-09 09:07 -0700
Re: Implementing virtual memory on cassette tape chitselb <chitselb@gmail.com> - 2012-08-09 12:20 -0700
Re: Implementing virtual memory on cassette tape Mat <dambere@web.de> - 2012-08-10 13:41 -0700
Re: Implementing virtual memory on cassette tape Coos Haak <chforth@hccnet.nl> - 2012-08-10 23:54 +0200
Re: Implementing virtual memory on cassette tape dambere@web.de - 2012-08-10 15:41 -0700
Re: Implementing virtual memory on cassette tape Coos Haak <chforth@hccnet.nl> - 2012-08-11 01:47 +0200
Re: Implementing virtual memory on cassette tape Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-08-11 03:50 -0500
Re: Implementing virtual memory on cassette tape anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-08-11 09:03 +0000
Re: Implementing virtual memory on cassette tape Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-08-11 16:08 -0500
Re: Implementing virtual memory on cassette tape "Elizabeth D. Rather" <erather@forth.com> - 2012-08-11 21:51 -1000
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