Lennart Sorensen wrote:
On Mon, Apr 16, 2007 at 10:18:45PM +0200, Tomasz K?oczko wrote:
Of cources it can be true in most cases (probably for some more advanced
RAID controlers). Few weeks ago I perform some basic test on Dell 2950
with 8x73GB SAS disk .. just as for kill time (waiting for access to some
bigger box ;). This small iron box have inside RAID controller (Dell uses
in this box LSI Logic SAS MegaRAID based ctrl). Anykind combinations on
controler level RAID was slower than using this as plain JBOD with LVM or
MD+LVM. Diffrence between HW and soft RAID was not so big (1-6% depending
on configuration) but allways HW produces worser results (don't ask me
why). Finaly I decide using this disk as four RAID1 luns only because
under Linux I can't read each phisical disk SMART data and protecting this
by RAID on controller level and collecting SNMP traps from DRAC card was
kind of worakaround for this (in my case it will be better constanlty
monitor disk healt and collesting some SMART data for observe trends on
for example zabbix graphs for try predict some faults using triggers). On
top of this was configured diffrent types of volumes on LVM level (some
with stripping some without, some with bigger some with smaller chunk
size).
Does it matter that google's recent report on disk failures indicated
that SMART never predicted anything useful as far as they could tell?
Certainly none of my drive failures ever had SMART make any kind of
indication that anything was wrong.
I think the main benefit of MD raid, is that it is portable, doesn't
lock you into a specific piece of hardware, and you can span multiple
controllers, and it is likely easier to have bugs in MD raid fixed that
in some raid controller's firmware if any were to be found. Performance
advantages are a bonus of course.
SMART largely depends on how you use it. Simply polling the current
status will not give you all the benefits SMART provides. On the
dedicated servers that I rent, running the extended test ('-t long')
often finds problems before you start losing data, or deal with a drive
death. Certainly not a huge sample size, but it backs up what I hear in
the field. Running the SMART tests on a weekly basis seems most
effective, though you'll want to stagger the tests if running in a RAID set.
Jeff
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
