[CentOS] stripe size for SSDs? ( cyrus spool on btrfs?)

Wed Sep 13 16:21:01 UTC 2017
Stephen John Smoogen <smooge at gmail.com>

On 13 September 2017 at 12:00, hw <hw at gc-24.de> wrote:

>> It will depend on the type of SSD. Ones with large cache and various
>> smarts (SAS Enterprise type) can take many different sizes. For SATA
>> ones it depends on what the cache and write of the SSD is and very few
>> of them seem to be the same. The SSD also has all kinds of logic which
>> moves data around constantly on disk to wipe level so it makes it
>> opaque. The people who have tested this usually have to burn through
>> an SSD set to get an idea about a particular 'run' of a model but it
>> doesn't go over every version of the model of SATA SSD.
> Hm, so much to SSDs ...  I can only hope they will be replaced with
> something better.
> I have decided against putting anything onto these SSDs other than temporary
> data, but even for that, I would need to make an md-RAID, which I don´t
> want.
> It may work or not, and "may work" is not enough.

May work is part of any commodity hardware build. The SATA hard drives
do not use the same technology as 4 years ago and you may end up with
them having crap out on shorter lifetimes because they aren't built to
live longer than 3 years depending on the model. [It doesn't matter
the brand.. they get built with the same tech and at the same place
these days.]

> If the performance on the hardware RAID isn´t as good, it can not get worse
> than it is now, and it may be even better than with the SSDs.
> I have two at home with the system installed on btrfs.  I´m going to change
> that
> to md-RAID1 and xfs.  Is there anything special involved in copying the
> system
> to another disk?  Will 'cp -ax' do, or should I use rsync to copy xattrs
> etc.?
> Using the commonly used stripe size of 128kb is something I´d expect the
> SSDs
> being able to handle.

Depending on what CentOS you are working, cp -a will preserve xattrs.

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Stephen J Smoogen.