ZFS gurus,
Consider this scenario: Lets say I put a cost-effective RAM disk[1] (with
battery backup) card into a Solaris system and I wish to use it as the
primary storage device that''ll be used for heavy I/O - possibly
involving a
large number of small file create/use/delete type operations. But I''d
like
this RAM disk to be backed up by a mirror device. And, of course, I''d
like
these to be part of a zfs mirror.
Ques: Is there any way that I could "tell" ZFS to unequally
"favor" the RAM
disk - in terms of read/writes. Especially in terms of reads. For
example, instead of a 1:1 round-robin read of the RAM/rotating-media disk
device, I might like it to be 10:1 or 20:1, so that the majority of the
operations take place on the RAM disk. Essentially the other half of the
mirror, in this case a real disk drive, is simply a "backup" in case
the
RAM disk drive dies or the firmware freezes up.
I know that this can be done by taking periodic snapshots and storing them
to non-volatile storage. But that does not seem to be exactly what I''m
trying to achieve.
Looking into my personal crystal ball, it appears that we''ll see many
more
cost-effective RAM disk drive devices appearing in the marketplace and that
the speed/capacity of those devices will increase pretty dramatically over
the next couple of years.
[1] Emulates an SATA disk drive:
1 * Gigabyte GC-RAMDISK approx $143.99
4 * Memory 1Gb Kingston D400 KVR400X64C3A/1G approx $77.81 each
PS: I intend to test 2 of these devices in a zfs mirror RSN (Real Soon
Now).
Regards,
Al Hopper Logical Approach Inc, Plano, TX. al at logical-approach.com
Voice: 972.379.2133 Fax: 972.379.2134 Timezone: US CDT
OpenSolaris.Org Community Advisory Board (CAB) Member - Apr 2005
Hello Al,
Saturday, April 15, 2006, 12:34:40 AM, you wrote:
AH> ZFS gurus,
AH> Consider this scenario: Lets say I put a cost-effective RAM disk[1] (with
AH> battery backup) card into a Solaris system and I wish to use it as the
AH> primary storage device that''ll be used for heavy I/O - possibly
involving a
AH> large number of small file create/use/delete type operations. But
I''d like
AH> this RAM disk to be backed up by a mirror device. And, of course,
I''d like
AH> these to be part of a zfs mirror.
AH> Ques: Is there any way that I could "tell" ZFS to unequally
"favor" the RAM
AH> disk - in terms of read/writes. Especially in terms of reads. For
AH> example, instead of a 1:1 round-robin read of the RAM/rotating-media disk
AH> device, I might like it to be 10:1 or 20:1, so that the majority of the
AH> operations take place on the RAM disk. Essentially the other half of the
AH> mirror, in this case a real disk drive, is simply a "backup" in
case the
AH> RAM disk drive dies or the firmware freezes up.
Right now you can do it with SVM (man metaparam).
Well in theory it should even work with ZFS on top of SVM.
But I know - it could be useful to have such feature completly in ZFS
(it could be better) - I just wanted to point out that if you really
need this right now you can do it with SVM.
--
Best regards,
Robert mailto:rmilkowski at task.gda.pl
http://milek.blogspot.com