zfs discuss - Jul 2010 - block align SSD for use as a l2arc cache

I have an Intel X25-M 80GB SSD.

 

For optimum performance, I need to block align the SSD device, but I am not
sure exactly how I should to it.  

 

If I run the format -> fdisk it allows me to partition based on a cylinder,
but I don''t think that is sufficient enough.

 

Can someone tell me how they block aligned an SSD device for use in l2arc.

 

Thanks,

 

Geoff 

 

 

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On 7/9/2010 5:55 PM, Geoff Nordli wrote:
>
> I have an Intel X25-M 80GB SSD.
>
> For optimum performance, I need to block align the SSD device, but I 
> am not sure exactly how I should to it.
>
> If I run the format -> fdisk it allows me to partition based on a 
> cylinder, but I don''t think that is sufficient enough.
>
> Can someone tell me how they block aligned an SSD device for use in l2arc.
>
> Thanks,
>
> Geoff
>
>
(a) what makes you think you need to do block alignment for an L2ARC 
usage (particularly if you give the entire device to ZFS)?

(b) what makes you think that even if (a) is needed, that ZFS will 
respect 4k block boundaries? That is, why do you think that ZFS would 
put any effort into doing block alignment with its L2ARC writes?

-- 
Erik Trimble
Java System Support
Mailstop:  usca22-123
Phone:  x17195
Santa Clara, CA

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>-----Original Message-----
>From: Erik Trimble  
>Sent: Friday, July 09, 2010 6:45 PM
>Subject: Re: [zfs-discuss] block align SSD for use as a l2arc cache
>
>On 7/9/2010 5:55 PM, Geoff Nordli wrote:
>I have an Intel X25-M 80GB SSD.
>
>For optimum performance, I need to block align the SSD device, but I am not
sure
>exactly how I should to it.
>
>If I run the format -> fdisk it allows me to partition based on a
cylinder,
but I don''t
>think that is sufficient enough.
>
>Can someone tell me how they block aligned an SSD device for use in l2arc.
>
>Thanks,
>
>Geoff
>
>
>(a) what makes you think you need to do block alignment for an L2ARC usage
>(particularly if you give the entire device to ZFS)?
>
>(b) what makes you think that even if (a) is needed, that ZFS will respect
4k block
>boundaries? That is, why do you think that ZFS would put any effort into
doing
>block alignment with its L2ARC writes?
>
Thanks Erik.

So obviously what you are saying is you don''t need to worry about doing
block alignment with an l2arc cache device because it will randomly
read/write at the device block level instead of doing a larger writes like a
file system.   

Have a great weekend!

Geoff