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* Re: [9fans] Petabytes on a budget: JBODs + Linux + JFS
@ 2009-09-14 16:43 erik quanstrom
  2009-09-20 20:13 ` Bakul Shah
  0 siblings, 1 reply; 42+ messages in thread
From: erik quanstrom @ 2009-09-14 16:43 UTC (permalink / raw)
  To: 9fans

> I am going to try my hands at beating a dead horse:)
> So when you create a Venti volume, it basically writes '0's' to all the
> blocks of the underlying device right?  If I put a venti volume on a AoE
> device which is a linux raid5, using normal desktop sata drives, what
> are my chances of a successful completion of the venti formating (let's
> say 1TB raw size)?

drive mfgrs don't report write error rates.  i would consider any
drive with write errors to be dead as fried chicken.  a more
interesting question is what is the chance you can read the
written data back correctly.  in that case with desktop drives,
you have a
	8 bits/byte * 1e12 bytes / 1e14 bits/ure = 8%
i'm a little to lazy to calcuate what the probabilty is that
another sector in the row is also bad.  (this depends on
stripe size, the number of disks in the raid, etc.)  but it's
safe to say that it's pretty small.  for a 3 disk raid 5 with
64k stripes it would be something like
	8 bites/byte * 64k *3 / 1e14 = 1e-8
i'm making the completely unwarrented assumption that
read errors are independent, see below as to why they not
be.

> Have you ever encountered such problems, or are you
> using more robust hardware?

yes.  i have.  after unexpected power failure and apparently
a head crash, i have seen writes that appear to work but don't
followed by write failure and smart "threshold exceeded".
smart here isn't diagnostic but it allows one to rma a drive
without booting the drive wiz-bang tool.

- erik



^ permalink raw reply	[flat|nested] 42+ messages in thread
* [9fans] Petabytes on a budget: JBODs + Linux + JFS
@ 2009-09-04  0:53 Roman V Shaposhnik
  2009-09-04  1:20 ` erik quanstrom
  0 siblings, 1 reply; 42+ messages in thread
From: Roman V Shaposhnik @ 2009-09-04  0:53 UTC (permalink / raw)
  To: Fans of the OS Plan 9 from Bell Labs

"None of those technologies [NFS, iSCSI, FC] scales as cheaply,
reliably, goes as big, nor can be managed as easily as stand-alone pods
with their own IP address waiting for requests on HTTPS."
   http://blog.backblaze.com/2009/09/01/petabytes-on-a-budget-how-to-build-cheap-cloud-storage/

Apart from the obvious comment that I swear I used a quote like that
to justify 9P more than once, I'm very curious to know how Plan9
would perform on such a box.

Erik, do you have any comments?

Thanks,
Roman.




^ permalink raw reply	[flat|nested] 42+ messages in thread

end of thread, other threads:[~2009-09-22 10:59 UTC | newest]

Thread overview: 42+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2009-09-14 16:43 [9fans] Petabytes on a budget: JBODs + Linux + JFS erik quanstrom
2009-09-20 20:13 ` Bakul Shah
2009-09-21  3:37   ` erik quanstrom
2009-09-21 17:43     ` Bakul Shah
2009-09-21 18:02       ` erik quanstrom
2009-09-21 18:49         ` Wes Kussmaul
2009-09-21 19:21           ` erik quanstrom
2009-09-21 20:57             ` Wes Kussmaul
2009-09-21 22:42               ` erik quanstrom
2009-09-22 10:59             ` matt
2009-09-21 19:10         ` Bakul Shah
2009-09-21 20:30           ` erik quanstrom
2009-09-21 20:57             ` Jack Norton
2009-09-21 23:38               ` erik quanstrom
2009-09-21 22:07             ` Bakul Shah
2009-09-21 23:35               ` Eris Discordia
2009-09-22  0:45                 ` erik quanstrom
     [not found]               ` <6DC61E4A6EC613C81AC1688E@192.168.1.2>
2009-09-21 23:50                 ` Eris Discordia
  -- strict thread matches above, loose matches on Subject: below --
2009-09-04  0:53 Roman V Shaposhnik
2009-09-04  1:20 ` erik quanstrom
2009-09-04  9:37   ` matt
2009-09-04 14:30     ` erik quanstrom
2009-09-04 16:54     ` Roman Shaposhnik
2009-09-04 12:24   ` Eris Discordia
2009-09-04 12:41     ` erik quanstrom
2009-09-04 13:56       ` Eris Discordia
2009-09-04 14:10         ` erik quanstrom
2009-09-04 18:34           ` Eris Discordia
     [not found]       ` <48F03982350BA904DFFA266E@192.168.1.2>
2009-09-07 20:02         ` Uriel
2009-09-08 13:32           ` Eris Discordia
2009-09-04 16:52   ` Roman Shaposhnik
2009-09-04 17:27     ` erik quanstrom
2009-09-04 17:37       ` Jack Norton
2009-09-04 18:33         ` erik quanstrom
2009-09-08 16:53           ` Jack Norton
2009-09-08 17:16             ` erik quanstrom
2009-09-08 18:17               ` Jack Norton
2009-09-08 18:54                 ` erik quanstrom
2009-09-14 15:50                   ` Jack Norton
2009-09-14 17:05                     ` Russ Cox
2009-09-14 17:48                       ` Jack Norton
2009-09-04 23:25   ` James Tomaschke

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