[OpenIndiana-discuss] Good SLOG devices?

[wessels]

please look at this excellent paper:
http://www.ddrdrive.com/zil_accelerator.pdf

and a nice blog entry about the subject:
http://constantin.glez.de/blog/2010/07/solaris-zfs-synchronous-writes-and-zil-explained

To summarize:
-dram doesn't wear out, is much faster in latency and iops.
-any device which doesn't some backup power supply to write out any
lingering data can cause a lot off trouble
-(most if not all) SSDs aren't really designed for this kind of workload
-no dram device exists in a 3.5" nor 2.5" drive formfactor, so no JBOD
and no multipathing and no HA

In the dram corner:
-DDRdrive X1, a $2000 pcie card which can handle almost any load.
Excellent support for Solaris.
-ACARD 9010 or 9010B, a 300 to 400 euro 51/4 drivebay,  with a sata
connection. A bit odd but works perfect. No drivers, it's a small sata
disk. A metalwork shop made a custom rail for me to mount them inside
a chassis.

-In the SSD-with-battery corner:
-the very hard to obtain, one and only: STEC ZEUS aka LogZilla These
were/are the slog sold by Sun.
-most "enterprise versions" based on a SandForce controller. Not much
known on how they behave in real life and espescially how long...

-In the SSD without battery corner:
-The Intel X25E. Decent performer but I know of a place which wears
them out in a couple of months
-Anything without a battery is probably a waste of money anyway. The
whole goal is that the log is on STABLE storage. When the storage lies
about that you can as well turn the zil of in the first place. And
hope that your ups keeps the system up long enough and that your
system doesn't crash. The result of a powerloss is the same as when
your slog lies about committed writes.

regards,

frederik

On Tue, Mar 1, 2011 at 8:24 PM, Roy Sigurd Karlsbakk <roy at karlsbakk.net> wrote:
>> Next gen spec sheets suggest the X25-E will get a "Power Safe Write
>> Cache," something it does not have today.
>>
>> See:
>> http://www.anandtech.com/Show/Index/3965?cPage=5&all=False&sort=0&page=1&slug=intels-3rd-generation-x25m-ssd-specs-revealed
>>
>> (Article is about X25-M, scroll down for X25-E info.)
>
> 5k IOPS for write isn't very good for SLOGs, comparing to those 50k+ drives available.....
>
> Vennlige hilsener / Best regards
>
> roy
> --
> Roy Sigurd Karlsbakk
> (+47) 97542685
> roy at karlsbakk.net
> http://blogg.karlsbakk.net/
> --
> I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med fremmed opprinnelse. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk.
>
> _______________________________________________
> OpenIndiana-discuss mailing list
> OpenIndiana-discuss at openindiana.org
> http://openindiana.org/mailman/listinfo/openindiana-discuss
>