[NTLUG:Discuss] compression and Filesystem question

[Bryan J. Smith]

> As it pertains to using cheap IDE drives in SCSI converter trays

Ouch.  Not my preferred "reliable" setup but that's just me.

> for offsite storage and nearline archival storage....

Any reason you aren't considering adding a new storage controller like a
3Ware Escalade?  Shouldn't really cost anymore than the converters.

> 1.) Is there a file compression file-type that can be mounted as a
> filesystem?  Can one mount a tarred.gz?

Use the "conv=auto" option to mount.  Not sure if you have to mount it
on loopback.

>  What about a compressed ISO?  I guess read only would work.

ISO9660 is a pre-mastered filesystem format, so yes, it's largely read-only.
There were tools such as "growfs" that allowed DVD+RW to get around that.

UDF is its replacement which supports both pre-mastered (record) and read/write
(packet write) modes of CD-R/RW.  I've been using UDF on Linux with DVD-RAM
since 1998 (back when the drives were $500 for 2.6GB/side ;-).

> 2) Are there any file compression programs that will ABORT and just
> STORE a file if the file compression utility can not compress the file
> by $X%? Didn't/doesn't ZIP compression do something like that?

LZO (lzop) does.  It tests the first few blocks for compressor and stores
whole if it does not improve size.  Unfortunately I don't see kernel support
for LZO yet, even though it's GPL (but not BSD or LGPL, small note FYI).

> 3)  Has anyone ever hot swapped a software raid set? Can it be done? 

I recommend LVM when you use MD.  LVM stores all sorts of stuff that the
legacy PC BIOS disk label (i.e., Primary/Logical style) cannot.

> How does Linux handle the hot swapping of multiple 'three drive hardware
> RAID-5 disk sets'?

Everytime I've tried to use MD to do such, I dork it up when I test it.
Now that was with the older "raidtools" approach and not the newer 
"mdadm", but I typically just use 3Ware Escalade cards these days for any
serious ATA RAID.


-- 
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   Windows Enthusisats call me anti-Microsoft.
 They both must be correct because I have over a
decade of experience with both in mission critical
environments, resulting in a bigotry dedicated to
 mitigating risk and focusing on technologies ...
           not products or vendors
--------------------------------------------------
Bryan J. Smith, E.I.            b.j.smith at ieee.org