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From: Duncan <1i5t5.duncan@cox.net>
To: linux-btrfs@vger.kernel.org
Subject: Re: 1 week to rebuid 4x 3TB raid10 is a long time!
Date: Mon, 21 Jul 2014 02:48:46 +0000 (UTC)	[thread overview]
Message-ID: <pan$7b757$4788e010$b65976c7$4d1c0bad@cox.net> (raw)
In-Reply-To: 37e3a8cf8b7439d5cd2745b5efb9d37f.squirrel@webmail.wanet.net

ashford posted on Sun, 20 Jul 2014 12:59:21 -0700 as excerpted:

> If you assume a 12ms average seek time (normal for 7200RPM SATA drives),
> an 8.3ms rotational latency (half a rotation), an average 64kb write and
> a 100MB/S streaming write speed, each write comes in at ~21ms, which
> gives us ~47 IOPS.  With the 64KB write size, this comes out to ~3MB/S,
> DISK LIMITED.

> The 5MB/S that TM is seeing is fine, considering the small files he says
> he has.

Thanks for the additional numbers supporting my point. =:^)

I had run some of the numbers but not to the extent you just did, so I 
didn't know where 5 MiB/s fit in, only that it wasn't entirely out of the 
range of expectation for spinning rust, given the current state of 
optimization... or more accurately the lack thereof, due to the focus 
still being on features.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman


  reply	other threads:[~2014-07-21  2:49 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-07-20  8:45 1 week to rebuid 4x 3TB raid10 is a long time! TM
2014-07-20 13:53 ` Duncan
2014-07-20 14:00   ` Tomasz Torcz
2014-07-20 14:50     ` Austin S Hemmelgarn
2014-07-20 17:15     ` ashford
2014-07-20 18:21       ` TM
2014-07-20 18:23       ` TM
2014-07-20 19:15 ` Bob Marley
2014-07-20 19:36   ` Roman Mamedov
2014-07-20 19:59     ` ashford
2014-07-21  2:48       ` Duncan [this message]
2014-07-21 16:46         ` ronnie sahlberg
2014-07-21 18:31           ` Chris Murphy
2014-07-22  2:51           ` Duncan
2014-07-22 17:13             ` Chris Murphy
2014-07-24 17:19               ` Chris Murphy
2014-07-20 21:28     ` Bob Marley
2014-07-20 21:54       ` George Mitchell
2014-07-21  1:22 ` Wang Shilong
2014-07-21 14:00   ` TM
2014-07-22  1:10     ` Wang Shilong
2014-07-22  1:17     ` Wang Shilong
2014-07-22 14:43       ` TM
2014-07-22 15:30         ` Stefan Behrens
2014-07-22 20:21           ` TM

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