From: Grant <emailgrant@gmail.com>
To: Gentoo mailing list <gentoo-user@lists.gentoo.org>
Subject: Re: [gentoo-user] Re: ZFS
Date: Thu, 19 Sep 2013 13:01:46 +0000 [thread overview]
Message-ID: <CAN0CFw1mhkTqOCxvDZ4g8O65fPoLSPg-8ZvrQ9g-30h6uo7Czg@mail.gmail.com> (raw)
In-Reply-To: <CAA2qdGUR3wVCRqwUp=CNyh-Pambjq3CVGR3iZY0_XSbC76ptyA@mail.gmail.com>
>>> You should definitely determine the right value for ashift on pool
>>> creation
>>> (it controls the alignment on the medium). It's an option that you afaik
>>> can only set
>>> on filesystem creation and therefore needs a restart from scratch if you
>>> get it
>>> wrong.
>>> According to the illumos wiki it's possible to run a mixed pool (if you
>>> have
>>> drives requiring different alignments[1])
>>> If in doubt: ask ryao (iirc given the right information he can tell you
>>> which
>>> are the right options for you if you can't deduce it yourself).
>>> Choosing the wrong alignment can cause severe performance loss (that's not
>>> a ZFS issue but happened when 4k sector drives appeared and tools like
>>> fdisk
>>> weren't aware of this).
>>
>> Yikes...
>>
>> Ok, shouldn't there be a tool or tools to help with this? Ie, boot up on a
>> bootable tools disk on the system with all drives connected, then let it
>> 'analyze' your system, maybe ask you some questions (ie, how you will be
>> configuring the drives/RAID, etc), then spit out an optimized config for
>> you?
>>
>> It is starting to sound like you need to be a dang engineer just to use
>> ZFS...
>>
>
> Just do ashift=12 and you're good to go. No need to analyze further.
>
> The reason I said that because in the future, *all* drives will have 4
> KiB sectors. Currently, many drives still have 512 B sectors. But when
> one day your drive dies and you need to replace it, will you be able
> to find a drive with 512 B sectors?
>
> Unlikely.
>
> That's why, even if your drives are currently of the 'classic' 512 B
> ones, go with ashift=12 anyway.
>
> For SSDs, the situation is murkier. Many SSDs 'lie' about their actual
> sector size, reporting to the OS that their sector size is 512 B (or 4
> KiB). No tool can pierce this veil of smokescreen. The only way is to
> do research on the Internet.
OK, so figure out what SSD you're using and Google to find the correct ashift?
- Grant
next prev parent reply other threads:[~2013-09-19 13:02 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-17 7:20 [gentoo-user] ZFS Grant
2013-09-17 7:36 ` Marc Stürmer
2013-09-17 8:05 ` Pandu Poluan
2013-09-17 8:22 ` Alan McKinnon
2013-09-17 9:44 ` Grant
2013-09-17 9:42 ` Grant
2013-09-17 10:11 ` Tanstaafl
2013-09-17 16:32 ` covici
2013-09-19 22:41 ` Douglas J Hunley
2013-09-20 23:12 ` Hinnerk van Bruinehsen
2013-09-19 22:46 ` Douglas J Hunley
2013-09-17 9:52 ` Joerg Schilling
2013-09-17 13:22 ` Grant
2013-09-17 13:30 ` Joerg Schilling
2013-09-17 16:39 ` Alan McKinnon
2013-09-18 4:06 ` Grant
2013-09-17 10:19 ` Tanstaafl
2013-09-17 13:21 ` Grant
2013-09-17 15:18 ` Michael Orlitzky
2013-09-17 15:40 ` Tanstaafl
2013-09-17 16:34 ` Michael Orlitzky
2013-09-17 17:00 ` Tanstaafl
2013-09-17 17:07 ` Michael Orlitzky
2013-09-17 17:34 ` Tanstaafl
2013-09-17 17:54 ` Stefan G. Weichinger
2013-09-18 4:11 ` Grant
2013-09-18 7:26 ` Stefan G. Weichinger
2013-09-18 15:17 ` Stefan G. Weichinger
2013-09-19 22:46 ` Douglas J Hunley
2013-09-20 9:17 ` Joerg Schilling
2013-09-20 11:17 ` Tanstaafl
2013-09-18 4:02 ` Grant
2013-09-17 18:00 ` Volker Armin Hemmann
2013-09-17 18:11 ` covici
2013-09-17 19:30 ` Volker Armin Hemmann
2013-09-18 4:20 ` Grant
2013-09-20 18:20 ` Grant
2013-09-20 23:07 ` Hinnerk van Bruinehsen
2013-09-21 4:34 ` Grant
2013-09-17 18:11 ` Tanstaafl
2013-09-17 19:30 ` Volker Armin Hemmann
2013-09-18 4:22 ` Bruce Hill
2013-09-18 8:03 ` Neil Bothwick
2013-09-18 12:55 ` [gentoo-user] ZFS James
2013-09-19 4:49 ` Grant
2013-09-19 7:43 ` Pandu Poluan
2013-09-19 7:44 ` Hinnerk van Bruinehsen
2013-09-19 7:47 ` Pandu Poluan
2013-09-19 8:04 ` Stefan G. Weichinger
2013-09-19 13:04 ` Grant
2013-09-19 10:37 ` Tanstaafl
2013-09-19 12:29 ` Grant
2013-09-19 12:54 ` Pandu Poluan
2013-09-19 13:01 ` Grant [this message]
2013-09-19 13:12 ` Pandu Poluan
2013-09-18 4:12 ` [gentoo-user] ZFS Grant
2013-09-18 9:56 ` Joerg Schilling
2013-09-18 17:04 ` Volker Armin Hemmann
2013-09-19 4:47 ` Grant
2013-09-20 15:11 ` Volker Armin Hemmann
2013-09-18 13:53 ` Stefan G. Weichinger
2013-09-19 1:02 ` Dale
2013-09-19 4:44 ` Grant
2013-09-19 7:40 ` Dale
2013-09-19 7:45 ` Pandu Poluan
2013-09-19 9:07 ` Joerg Schilling
2013-09-19 11:22 ` Dale
2013-09-19 11:27 ` Joerg Schilling
2013-09-22 1:19 ` Dale
2013-09-19 9:04 ` Joerg Schilling
2013-09-21 12:53 ` thegeezer
2013-09-21 16:49 ` Pandu Poluan
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