[Lustre-discuss] MDS failover: SSD+DRDB or shared 15K-SAS-Storage RAID with approx. 10 disks

[Carlos Thomaz]

Hi Michael,

In my experience SSDs didn't help much, since the MDS bottleneck is not
only a disk problem rather than the entire lustre metadata mechanism.
We've been configuring highly scalable systems, lots of them with a high
IOPS demand, using RAID controllers and fast disks as you stated (usually
SAS 15K RPM, usually RAID10). It's difficult to to size it without knowing
exactly your I/O pattern and workload, but if you would like more
information about current systems and metadata benchmark on raid
controllers, size and configuration, let us know.

One remark about DRDB: I've seen customers using it, but IMHO, if
Active/standby HA type configuration would be more reliable and will
provide you a better resilience. Again, don't know about your uptime and
reliability needs, but the customers I've worked with that requires
minimum downtime on production, always go for RAID controllers rather than
DRDB replication.

Regards,
Carlos.


--
Carlos Thomaz | Systems Architect
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On 1/22/12 12:04 PM, "Michael Kluge" <Michael.Kluge at tu-dresden.de> wrote:

>Hi,
>
>I have been asked, which one of the two I would chose for two MDS
>servers (active/passive). Whether I would like to have SSDs, maybe two
>(mirrored) in both servers and DRDB for synching, or a RAID controller
>that has a 15K disks. I have not done benchmarks on this topic myself
>and would like to ask if anyone has an idea or numbers? The cluster will
>be pretty small, about 50 clients.
>
>
>Regards, Michael
>
>-- 
>Dr.-Ing. Michael Kluge
>
>Technische Universität Dresden
>Center for Information Services and
>High Performance Computing (ZIH)
>D-01062 Dresden
>Germany
>
>Contact:
>Willersbau, Room WIL A 208
>Phone:  (+49) 351 463-34217
>Fax:    (+49) 351 463-37773
>e-mail: michael.kluge at tu-dresden.de
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