recommendations for SSD drive as first disk for fedora 18?

[Rick Stevens]

On 01/22/2013 10:51 AM, Bill Davidsen issued this missive:
> Sergio Augusto Vladisauskis wrote:
>> Look this topic:
>> http://thessdreview.com/Forums/linux/225-post2940.htm#post2940
>> I using Fedora 17 with this options.
>>
>> PS: my logs put in other HD.
>>
> Always good to get another view, however I would like to see a better
> explanation of what those changes do before just telling people to do
> them (him, not you).
>
> in no order:
>
> deadline scheduler works for SSD (and most types of RAID) but I did't
> see any big gain so I general l don't bother.
>
> Having /tmp be really temporary can lead to having to find a better
> place to put stuff you need for a few days, and putting it in RAM
> requires enough memory to match what you would use on disk. In my case
> that's a few GB, but everyone has a different idea of what it should do,
> so understand the results before you decide faster is always better.
>
> I want to test what setting fifo_batch is going to do before I comment
> on that. There is no such value in RHEL5 or FC17 on my machines:
>     ls -lG /sys/block/sda/queue/iosched/
>     total 0
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 back_seek_max
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 back_seek_penalty
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 fifo_expire_async
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 fifo_expire_sync
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 group_idle
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 low_latency
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 quantum
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 slice_async
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 slice_async_rq
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 slice_idle
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 slice_sync
>     -rw-r--r--. 1 root 4096 Jan 22 13:38 target_latency
> so I want to go look at the kernel code and description to see what that
> does and what side effects it might have.
>
> Changing the elevator=deadline option on the kernel command line will
> change it for all drives, not just the SSD. That may really not what you
> want for performance on non-RAID drives.
>
> The techniques are good to know, but I hope people do understand the
> side effects of some of these things.

And please, PLEASE make sure you have a reliable and consistent backup
procedure. I like SSDs, but when they die they generally die
catastrophically and completely (at least in my experience) and you may
not be able to recover anything from them.

Standard drives tend to get "flakey" as they spiral down the drain and
you may have enough time to get a backup off them before they
completely croak.

Just saying......
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- Rick Stevens, Systems Engineer, AllDigital    ricks at alldigital.com -
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