On Mon, 23 May 2011, Ray Van Dolson wrote:
> To: centos@xxxxxxxxxx
> From: Ray Van Dolson <rayvd@xxxxxxxxxxxx>
> Subject: Re: SSD for Centos SWAP /tmp & /var/ partition
>
> On Mon, May 23, 2011 at 02:29:22PM -0500, Robert Nichols wrote:
>> On 05/23/2011 01:44 PM, Jerry Franz wrote:
>>>
>>> But, for paranoia's sake, I would RAID1 the SSD with a second SSD.
>>>
>>
>> Quote from
>> http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/newmds-ssdtuning.html
>> :
>>
>> Red Hat also warns that software RAID levels 1, 4, 5, and 6 are not
>> recommended for use on SSDs. During the initialization stage of these
>> RAID levels, some RAID management utilities (such as mdadm) write to
>> all of the blocks on the storage device to ensure that checksums
>> operate properly. This will cause the performance of the SSD to degrade
>> quickly.
>>
>
> Huh. Maybe LVM mirroring would be alright.
Quote from above link.
"In addition, keep in mind that MD (software raid) does not
support discards. In contrast, the logical volume manager
(LVM) and the device-mapper (DM) targets that LVM uses do
support discards. The only DM targets that do not support
discards are dm-snapshot, dm-crypt, and dm-raid45. Discard
support for the dm-mirror was added in Red Hat Enterprise
Linux 6.1."
It's not a very large article. A quick 5-10 minute read
maybe.
Keith
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