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From: Roberto Spadim <roberto@spadim.com.br>
To: "Keld Jørn Simonsen" <keld@keldix.com>
Cc: Drew <drew.kay@gmail.com>, Linux-RAID <linux-raid@vger.kernel.org>
Subject: Re: What's the typical RAID10 setup?
Date: Thu, 3 Feb 2011 13:54:54 -0200	[thread overview]
Message-ID: <AANLkTimznEe8Vm2HoYJyAPpjHLbp3AWMqmd68csSgQjB@mail.gmail.com> (raw)
In-Reply-To: <AANLkTinKHG0dE0BeXX3v1z9my4+jDLebc96vMHJpjHDB@mail.gmail.com>

sorry
/sys/block/md0/distance_rate -> /sys/block/md0/md/sda1_distance_rate
/sys/block/md0/byte_read_rate ->/sys/block/md0/md/sda1_byte_read_rate

2011/2/3 Roberto Spadim <roberto@spadim.com.br>:
> hummm, nice
> keld (or anyone), do you know someone (with time, not much, total time
> i think it´s just 2 hours) to try develop modifications on raid1
> read_balance function?
> what modification, today read_balance have distance (current_head -
> next_head), multiply it by a number at /sys/block/md0/distance_rate,
> and make add read_size*byte_rate (byte_rate at
> /sys/block/md0/byte_read_rate), with this, the algorithm will make
> minimal time, and not minimal distance
> with this, i can get better read_balance (for ssd)
> for a second time we could implement device queue time to end (i think
> we will work about 1 day to get it working with all device
> schedulers), but it´s not for now
>
>
> 2011/2/3 Keld Jørn Simonsen <keld@keldix.com>:
>> On Thu, Feb 03, 2011 at 12:35:52PM -0200, Roberto Spadim wrote:
>>> =] i think that we can end discussion and conclude that context (test
>>> / production) allow or don't allow lucky on probability, what's lucky?
>>> for production, lucky = poor disk, for production we don't allow
>>> failed disks, we have smart to predict, and when a disk fail we change
>>> many disks to prevent another disk fail
>>>
>>> could we update our raid wiki with some informations about this discussion?
>>
>> I would like to, but it is a bit complicated.
>> Anyway I think there already is something there on the wiki.
>> And then, for one of the most important raid types in Linux MD,
>> namely raid10, I am not sure what to write. It could be raid1+0, or
>> raid0+1 like, and as far as I kow, it is raid0+1 for F2:-(
>> but I don't know for n2 and o2.
>>
>> The German version on raid at wikipedia has a lot of info on probability
>> http://de.wikipedia.org/wiki/RAID - but it is wrong a number of places.
>> I have tried to correct it, but the German version is moderated, and
>> they don't know what they are writing about.
>> http://de.wikipedia.org/wiki/RAID
>>
>> Best regards
>> Keld
>>
>>> 2011/2/3 Drew <drew.kay@gmail.com>:
>>> >> for test, raid1 and after raid0 have better probability to don't stop
>>> >> raid10, but it's a probability... don't believe in lucky, since it's
>>> >> just for test, not production, it doesn't matter...
>>> >>
>>> >> what i whould implement? for production? anyone, if a disk fail, all
>>> >> array should be replaced (if without money replace disk with small
>>> >> life)
>>> >
>>> > A lot of this discussion about failure rates and probabilities is
>>> > academic. There are assumptions about each disk having it's own
>>> > independent failure probability, which if that can not be predicted
>>> > must be assumed to be 50%.  At the end of the day I agree that when
>>> > the first disk fails the RAID is degraded and one *must* take steps to
>>> > remedy that. This discussion is more about why RAID 10 (1+0) is better
>>> > then 0+1.
>>> >
>>> > On our production systems we work with our vendor to ensure the
>>> > individual drives we get aren't from the same batch/production run,
>>> > thereby mitigating some issues around flaws in specific batches. We
>>> > keep spare drives on hand for all three RAID arrays, so as to minimize
>>> > the time we're operating in a degraded state. All data on RAID arrays
>>> > is backed up nightly to storage which is then mirrored off-site.
>>> >
>>> > At the end of the day our decision around what RAID type (10/5/6) to
>>> > use was based on a balance between performance, safety, & capacity
>>> > then on specific failure criteria. RAID 10 backs the iSCSI LUN that
>>> > our VMware cluster uses for the individual OSes, and the data
>>> > partition for the accounting database server. RAID 5 backs the
>>> > partitions we store user data one. And RAID 6 backs the NASes we use
>>> > for our backup system.
>>> >
>>> > RAID 10 was chosen for performance reasons. It doesn't have to
>>> > calculate parity on every write so for the OS & database, which do a
>>> > lot of small reads & writes, it's faster. For user disks we went with
>>> > RAID 5 because we get more space in the array at a small performance
>>> > penalty, which is fine as the users have to access the file server
>>> > over the LAN and the bottle neck is the pipe between the switch & the
>>> > VM, not between the iSCSI SAN & the server. For backups we went with
>>> > RAID 6 because the performance & storage penalties for the array were
>>> > outweighed by the need for maximum safety.
>>> >
>>> >
>>> >
>>> > --
>>> > Drew
>>> >
>>> > "Nothing in life is to be feared. It is only to be understood."
>>> > --Marie Curie
>>> >
>>> >
>>>
>>>
>>>
>>> --
>>> Roberto Spadim
>>> Spadim Technology / SPAEmpresarial
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>>> the body of a message to majordomo@vger.kernel.org
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>> --
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>>
>
>
>
> --
> Roberto Spadim
> Spadim Technology / SPAEmpresarial
>



-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
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  reply	other threads:[~2011-02-03 15:54 UTC|newest]

Thread overview: 127+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-31  9:41 What's the typical RAID10 setup? Mathias Burén
2011-01-31 10:14 ` Robin Hill
2011-01-31 10:22   ` Mathias Burén
2011-01-31 10:36 ` CoolCold
2011-01-31 15:00   ` Roberto Spadim
2011-01-31 15:21     ` Robin Hill
2011-01-31 15:27       ` Roberto Spadim
2011-01-31 15:28         ` Roberto Spadim
2011-01-31 15:32           ` Roberto Spadim
2011-01-31 15:34             ` Roberto Spadim
2011-01-31 15:37               ` Roberto Spadim
2011-01-31 15:45             ` Robin Hill
2011-01-31 16:55         ` Denis
2011-01-31 17:31           ` Roberto Spadim
2011-01-31 18:35             ` Denis
2011-01-31 19:15               ` Roberto Spadim
2011-01-31 19:28                 ` Keld Jørn Simonsen
2011-01-31 19:35                   ` Roberto Spadim
2011-01-31 19:37                     ` Roberto Spadim
2011-01-31 20:22                     ` Keld Jørn Simonsen
2011-01-31 20:17                   ` Stan Hoeppner
2011-01-31 20:37                     ` Keld Jørn Simonsen
2011-01-31 21:20                       ` Roberto Spadim
2011-01-31 21:24                         ` Mathias Burén
2011-01-31 21:27                           ` Jon Nelson
2011-01-31 21:47                             ` Roberto Spadim
2011-01-31 21:51                               ` Roberto Spadim
2011-01-31 22:50                                 ` NeilBrown
2011-01-31 22:53                                   ` Roberto Spadim
2011-01-31 23:10                                     ` NeilBrown
2011-01-31 23:14                                       ` Roberto Spadim
2011-01-31 22:52                               ` Keld Jørn Simonsen
2011-01-31 23:00                                 ` Roberto Spadim
2011-02-01 10:01                                 ` David Brown
2011-02-01 13:50                                   ` Jon Nelson
2011-02-01 14:25                                     ` Roberto Spadim
2011-02-01 14:48                                     ` David Brown
2011-02-01 15:41                                       ` Roberto Spadim
2011-02-03  3:36                                         ` Drew
2011-02-03  8:18                                           ` Stan Hoeppner
     [not found]                                           ` <AANLkTikerSZfhMbkEvGBVyLB=wHDSHLWszoEz5As5Hi4@mail.gmail.com>
     [not found]                                             ` <AANLkTikLyR206x4aMy+veNkWPV67uF9r5dZKGqXJUEqN@mail.gmail.com>
2011-02-03 14:35                                               ` Roberto Spadim
2011-02-03 15:43                                                 ` Keld Jørn Simonsen
2011-02-03 15:50                                                   ` Roberto Spadim
2011-02-03 15:54                                                     ` Roberto Spadim [this message]
2011-02-03 16:02                                                     ` Keld Jørn Simonsen
2011-02-03 16:07                                                       ` Roberto Spadim
2011-02-03 16:16                                                       ` Roberto Spadim
2011-02-01 22:05                                     ` Stan Hoeppner
2011-02-01 23:12                                       ` Roberto Spadim
2011-02-02  9:25                                         ` Robin Hill
2011-02-02 16:00                                           ` Roberto Spadim
2011-02-02 16:06                                             ` Roberto Spadim
2011-02-02 16:07                                               ` Roberto Spadim
2011-02-02 16:10                                                 ` Roberto Spadim
2011-02-02 16:13                                                   ` Roberto Spadim
2011-02-02 19:44                                                     ` Keld Jørn Simonsen
2011-02-02 20:28                                                       ` Roberto Spadim
2011-02-02 21:31                                                         ` Roberto Spadim
2011-02-02 22:13                                                         ` Keld Jørn Simonsen
2011-02-02 22:26                                                           ` Roberto Spadim
2011-02-03  1:57                                                             ` Roberto Spadim
2011-02-03  3:05                                                         ` Stan Hoeppner
2011-02-03  3:13                                                           ` Roberto Spadim
2011-02-03  3:17                                                             ` Roberto Spadim
2011-02-01 23:35                                       ` Keld Jørn Simonsen
2011-02-01 16:02                                   ` Keld Jørn Simonsen
2011-02-01 16:24                                     ` Roberto Spadim
2011-02-01 17:56                                       ` Keld Jørn Simonsen
2011-02-01 18:09                                         ` Roberto Spadim
2011-02-01 20:16                                           ` Keld Jørn Simonsen
2011-02-01 20:32                                     ` Keld Jørn Simonsen
2011-02-01 20:58                                       ` Roberto Spadim
2011-02-01 21:04                                         ` Roberto Spadim
2011-02-01 21:18                                     ` David Brown
2011-02-01  0:58                             ` Stan Hoeppner
2011-02-01 12:50                               ` Roman Mamedov
2011-02-03 11:04                               ` Keld Jørn Simonsen
2011-02-03 14:17                                 ` Roberto Spadim
2011-02-03 15:54                                   ` Keld Jørn Simonsen
2011-02-03 18:39                                     ` Keld Jørn Simonsen
2011-02-03 18:41                                       ` Roberto Spadim
2011-02-03 23:43                                 ` Stan Hoeppner
2011-02-04  3:49                                   ` hansbkk
2011-02-04  7:06                                   ` Keld Jørn Simonsen
2011-02-04  8:27                                     ` Stan Hoeppner
2011-02-04  9:06                                       ` Keld Jørn Simonsen
2011-02-04 10:04                                         ` Stan Hoeppner
2011-02-04 11:15                                           ` hansbkk
2011-02-04 13:33                                             ` Keld Jørn Simonsen
2011-02-04 20:35                                           ` Keld Jørn Simonsen
2011-02-04 20:42                                         ` Keld Jørn Simonsen
2011-02-04 21:15                                           ` Stan Hoeppner
2011-02-04 22:05                                             ` Keld Jørn Simonsen
2011-02-04 23:03                                               ` Stan Hoeppner
2011-02-06  3:59                                                 ` Drew
2011-02-06  4:27                                                   ` Stan Hoeppner
2011-02-04 11:34                                       ` David Brown
2011-02-04 13:53                                         ` Keld Jørn Simonsen
2011-02-04 14:17                                           ` David Brown
2011-02-04 14:21                                           ` hansbkk
2011-02-06  4:02                                             ` Drew
2011-02-06  7:58                                               ` Keld Jørn Simonsen
2011-02-06 12:03                                                 ` Roman Mamedov
2011-02-06 14:30                                                   ` Roberto Spadim
2011-02-01  8:46                             ` hansbkk
2011-01-31 19:37               ` Phillip Susi
2011-01-31 19:41                 ` Roberto Spadim
2011-01-31 19:46                   ` Phillip Susi
2011-01-31 19:53                     ` Roberto Spadim
2011-01-31 22:10                       ` Phillip Susi
2011-01-31 22:14                         ` Denis
2011-01-31 22:33                           ` Roberto Spadim
2011-01-31 22:36                             ` Roberto Spadim
2011-01-31 20:23                 ` Stan Hoeppner
2011-01-31 21:59                   ` Phillip Susi
2011-01-31 22:08                     ` Jon Nelson
2011-01-31 22:38                       ` Phillip Susi
2011-02-01 10:05                         ` David Brown
2011-02-01  9:20                     ` Robin Hill
2011-02-04 16:03                       ` Phillip Susi
2011-02-04 16:22                         ` Robin Hill
2011-02-04 20:35                           ` [OT] " Phil Turmel
2011-02-04 20:35                           ` Phillip Susi
2011-02-04 21:05                           ` Stan Hoeppner
2011-02-04 21:13                             ` Roberto Spadim
2011-01-31 15:30       ` Robin Hill
2011-01-31 20:07 ` Stan Hoeppner

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