Yes, I also read in P420 user guide that it was RAID only. We'll live
with it I guess...
Thanks for the HP/Cloudera link, it's precious reading !
Le 07/10/2014 08:52, Travis a écrit :
On Sun, Oct 5, 2014 at 4:17 PM, Ulul <[email protected]
<mailto:[email protected]>> wrote:
Hi Travis
Thank you for your detailed answer and for honoring my question
with a blog entry :-)
No problem. I had been meaning to write something up. Thanks for the
prod. :-)
I will look into bus quiescing with admins but I'm under the
impression that nothing special is done, the HW RAID controller
taking care of everything, HP doc stating that inserting a
hot-pluggable disk induces one or two seconds pause in disk
activity. I'll check whether this is handled through the
controller cache and/or done out of business hours for safety.
I'll ask for internal benchmarking hoping it will convince
everyone to accept the JBOD model and automate what's necessary
for it not to disrupt operations
Make sure your HP disk controllers can actually do JBOD. Last I
looked (admittedly, this was ~3 years ago), you could only simulate it
doing multiple single-disk RAID0 LUNs. Operationally, these were one
level annoying more than just JBOD because now you had to
remove/destroy the RAID0 LUN when replacing the disk before you could
recreate the filesystem.
At the very least, HP's reference architecture for Cloudera Hadoop
5.X, updated in August 2014, shows that this is still the case.
From their document:
Drives should use a Just a Bunch of Disks
(JBOD) configuration, which can be achieved with the HP Smart
Array P420i controller by configuring each individual disk as
a separate RAID 0 volume. Additionally array acceleration
features on the P420i should be turned off for the RAID 0 data
volumes. The first two positions on the drive cage allow the
OS drive to be placed in RAID1.
http://h20195.www2.hp.com/V2/GetDocument.aspx?docname=4AA5-3257ENW&cc=us&lc=en
If you've already got equipment, then probably not a big deal. If
you're in the process of evaluating new stuff, I'd ask your HP
Var/Reseller if there was a different, non-RAID option, especially if
they have something similar to the LSI-9207-8i card which uses the
LSI2308 SAS chip. I know Dell validated this with their 12G equipment
for use with Hadoop earlier this year. Definitely a great card so far.
Travis
--
Travis Campbell
[email protected] <mailto:[email protected]>
