[CentOS] raid resync speed? - laptop drive-

[Les Mikesell]

Robert Nichols wrote:
> On 05/22/2010 08:40 PM, Les Mikesell wrote:
>> Robert Nichols wrote:
>>> On 05/22/2010 07:39 PM, Robert Nichols wrote:
>>> I should add that the kernel normally will do I/O in multiples of its 4KB
>>> (typical) page size where possible, but I have no idea whether any effort
>>> is made to align those writes if the drive does not report a 4KB physical
>>> sector size, or whether it even makes sense to try beyond what the
>>> elevator algorithm does for coalescing sequential writes.
>>>
>>> I don't currently have any of these "enhanced format" drives, nor am I
>>> using RAID, so all I can report is the collected experience of others.
>> Well, the form factor is certainly nice.  I got a hot-swap carrier with 2 slots
>> that fits in a floppy bay and the drives themselves are tiny so it seemed ideal
>> for copies of data to go offsite.  I just wish it would work...  Even a dd at
>> the disk level seems slow so I'm not sure the writes are being aggregated even
>> if you ignore partitioning and offsets.
> 
> Another thing to keep in mind is that the SATA spec. only requires the
> internal SATA connector to withstand 50 insertions.  I picked up some
> nice acomdata (TM) eSATA housings for the drives (512-byte sectors,
> thankfully) I use for my offsite backup copies.  The eSATA connector
> is spec-ed for 50,000 insertions.  My laptop came with a warning about
> the life of that connector, and I found those ratings mentioned at
> http://www.serialata.org/technology/esata.asp .

The trayless internal hotswap enclosures claim to be good for 10,000+ insertions 
and I'm using larger ones for the desktop drives I had been using without any 
problems.   I have seen some postings to the effect that I need a newer kernel 
to recognize the 4k sectors besides doing the partition alignment.  Maybe I can 
boot the RHEL 6 beta or a fedora iso and see if they are faster.

-- 
   Les Mikesell
     lesmikesell at gmail.com