Hi Sean,
I sympathize with your intentions but providing pseudo-names for these
disks might cause more confusion than actual help.
The "c4t5..." name isn't so bad. I've seen worse. :-)
Here are the issues with using the aliases:
- If a device fails on a J4200, a LED will indicate which disk has
failed but will not identify the alias name.
- To prevent confusion with drive failures, you will need to map your
aliases to the disk names, possibly pulling out the disks and relabeling
them with the alias name. You might be able to use
/usr/lib/fm/fmd/fmtopo -V | grep disks to do these mappings online.
- We don't know what fmdump will indicate if a disk has problems, the
dev alias or the real disk name.
- We don't know what else might fail
The stress of mapping the alias names to real disk names, might happen
under duress, like when a disk fails. The physical disk ID on the disk
will be included in the expanded name, not the alias name.
The hardest part is getting the right disks in the pool. After that, it
gets easier. ZFS does a good job of identifying the devices in a pool
and will identify which disk is having problems as will the fmdump
command. The LEDs on the disks themselves also help disk replacements.
The wheels are turning to make device administration easier. We're just
not there yet.
Cindy
On 11/16/09 19:17, sean walmsley wrote:
We have a number of Sun J4200 SAS JBOD arrays which we have multipathed using Sun's MPxIO
facility. While this is great for reliability, it results in the /dev/dsk device IDs
changing from cXtYd0 to something virtually unreadable like
"c4t5000C5000B21AC63d0s3".
Since the entries in /dev/{rdsk,dsk} are simply symbolic links anyway, would there be any
problem with adding "alias" links to /devices there and building our zpools on
them? We've tried this and it seems to work fine producing a zpool status similar to the
following:
...
NAME STATE READ WRITE CKSUM
vol01 ONLINE 0 0 0
mirror ONLINE 0 0 0
top00 ONLINE 0 0 0
bot00 ONLINE 0 0 0
mirror ONLINE 0 0 0
top01 ONLINE 0 0 0
bot01 ONLINE 0 0 0
...
Here our aliases are "topnn" and "botnn" to denote the disks in the top and
bottom JBODs.
The obvious question is "what happens if the alias link disappears?". We've tested this,
and ZFS seems to handle it quite nicely by finding the "normal" /dev/dsk link and simply
working with that (although it's more difficult to get ZFS to use the alias again once it is
recreated).
If anyone can think of anything really nasty that we've missed, we'd appreciate
knowing about it. Alternatively, if there is a better supported means of having
ZFS display human-readable device ids we're all ears :-)
Perhaps an MPxIO RFE for "vanity" device names would be in order?
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