On 07/29/2011 10:55 AM, David Brown wrote:
One thing has occurred to me while reading this thread - it seems to be
an assumption here that SSD's are faster than HD's. In one area - access
times - SSD's are very much faster. But when transferring bulk data,
they are not necessarily faster.
Not necessarily, no. But, if you do like I did and pick your SSD
carefully, they are. I specifically chose the one I did because it was
SATA-III with a 6MB/s link speed and it was rated for 400+MByte/s reads
and 210MByte/s writes. Here's the link:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820233154
There are even faster ones out there now.
But, I was worried about the drive wearing out under the frequent
checkouts, builds, etc. so hence the reason I have two hard drives
backing it up. When it does wear out, I'll put a new one in, add it to
the array, wait for resync, all done.
Certainly a pair of good hard disks in
RAID10,far will stream reads and writes with a similar throughput to
many SSD's. An ideal situation is therefore that small reads will come
from the SSD, but that bulk reads could come from any disk that is
currently idle. Enabling "write-behind" on the hard disks would still be
a big gain on the write latency.
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