[CentOS] raid resync speed? - laptop drive-
Les Mikesell
lesmikesell at gmail.com
Sun May 23 18:57:53 UTC 2010
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
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