Re: [CentOS] SSD for Centos SWAP /tmp & /var/ partition

On 05/23/2011 12:27 PM, Ray Van Dolson wrote:

...

Quote from http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Ad... :

 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.

Not actually a problem if you are just using it for journaling. Journals max out at 400MB - so you are using only a tiny fraction of the entire SSD for the journal while getting a large performance pop on small writes since the OS can safely return to you before the data is actually written to the slower magnetic disk. Another alternative is to *not use the entire SSD*. Deliberately leave say 25% or so unallocated. Kind of like short stroking a disk for performance: You sacrifice capacity for speed.