ZFS disk replacement questions
arab at tangerine-army.co.uk
Sun Nov 15 01:19:32 UTC 2009
From: krad [mailto:kraduk at googlemail.com]
Sent: 04 November 2009 09:19
To: Steve Polyack
Cc: Derrick Ryalls; FreeBSD Questions
Subject: Re: ZFS disk replacement questions
2009/11/3 Steve Polyack <korvus at comcast.net>
> Derrick Ryalls wrote:
>> On Tue, Nov 3, 2009 at 10:21 AM, Steve Polyack <korvus at comcast.net>
>>> Derrick Ryalls wrote:
>>>> 1) In the event of a disk failure, how do I trace back the name
>>>> as adX to a physical drive in the enclosure? Is there a way to
>>>> the drive offline then use atacontrol to spin it down or something
>>>> it is easy to identify?
>>> In my opinion you are best off using glabel(8) to give names to the
>>> This way you can name them in a way that makes sense to you.
>>> when you create the ZFS pool you will use the glabel'd names. This
>>> that the pool will still come up properly if something causes your
>>> to be numbered differently (i.e. a drive dies and you happen to
>> I believe ZFS does this automatically. Supposedly, if you take a
>> working set of RAIDZ drives from one machine and put it in another,
>> ZFS will figure out the drives since they get labelled by ZFS
>> internally. My question concerns how to identify the physical disk
>> question based on the adX or glabel name? Different name in software
>> is fine, but if the drive fails I want to make sure I pull the
> This is possible, but I don't remember reading that ZFS handles this
> anywhere, and I've seen glabel(8) recommended elsewhere for the same
> Either way, you can add your drives one-by-one and label them on the
> enclosure "arraydrive00" and then glabel the individual disks with the
> name. This way when ZFS tells you "arraydrive03" is dead/offline, you
> look at your enclosure and pull the drive with the arraydrive03 label.
> Depending on your controller it is also probably worth it to use one
>>> SATA-specific drivers in FreeBSD 8 - these are ones like ahci(4) and
>>> siis(4). While the generic ata(4) driver will work for pretty much
>>> everything, the updated AHCI drivers can take advantage of some more
>>> features. Enable the modules at boot to use them.
>> I will look into it, thanks. The machine in question is 2 year old
>> hardware currently with a 3ware raid card. I will be going software
>> raid only, but FreeBSD already recognizes the eSATA drive I have
>> attached as a backup device so I know the O/S can at least talk to
>> sata drives attached to the mobo.
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One thing to note about resilvering; unlike most raid systems zfs knows
is going on at the filesystem level as well as block level. Therefore
drive has to be resilvered, only the data on the drive is rebuilt rather
than every block as with most other raid subsystems. eg if you have a
but only have 20 Gig of data, only 20 gig is copied/rebuilt rather than
of data if you were using gvinum/gmirror. This massively speeds up
times and stress on the other drives. However the fuller the drive the
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Sorry to jump in on someone else's question / answer but I have a
related query. I notice the previous answer mentioned specific achi(4)
driver and Freebsd 8.0 are these available in 7.2 ? Will the achi(4)
driver work happily along side the ata driver. I just replaced every
drive in my raidz array the dirty way as I could not see away to make
the replacement drive show up without doing a reboot, would the achi(4)
driver allow me to hot swap the disks in the future ?
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