|
Home > Archive > Data Storage > November 2006 > Re: MyISAM engine: worst case scenario in case of crash (mysql, O/S, hardware, whateve
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
Re: MyISAM engine: worst case scenario in case of crash (mysql, O/S, hardware, whateve
|
|
|
| Jerry Stuckle wrote:
> toby wrote:
>
> They will also handle hardware failures. I have never heard of any loss
> of data due to hardware failures on RAID-1 or RAID-10. Can you point to
> even one instance?
There are several examples of such hardware failures in the links
cited, but I'll crosspost this to comp.arch.storage - I'll eat my hat
if no-one there has seen a RAID data loss.
>
>
> Specifics? Using RAID-1 or RAID-10?
>
>
> And how does it recover from a disk crash? Or what happens if the data
> goes bad after being written and read back?
You use the redundancy to repair it. RAID-1 does not do this.
>
> Additionally, it depends on the software correctly detecting and
> signaling a data error.
Which RAID-1 cannot do at all.
>
>
> If it's a single sector. But if the entire disk crashes - i.e. an
> electronics failure?
That's right, it cannot bring a dead disk back to life...
>
> But all data is mirrored. And part of the drive's job is to signal
> errors. One which doesn't do that correctly isn't much good, is it/
You're right that RAID-1 is built on the assumption that drives
perfectly report errors. ZFS isn't.
As Richard Elling writes, "We don't have to rely on a parity protected
SCSI bus, or a bug-free disk firmware (I've got the scars) to ensure
that what is on persistent storage is what we get in memory. ... by
distrusting everything in the storage data path we will build in the
reliability and redundancy into the file system."
>
>
> So? I don't see anything in any of these articles which affects this
> discussion. We're not talking about long term digital storage, for
> instance.
I think that's quite relevant to many "business critical" database
systems. Databases are even evolving in response to changing
*regulatory* requirements: MySQL's ARCHIVE engine, for instance...
> I'm just curious. How many critical database systems have you actually
> been involved with? I've lost count. ...
> These systems are critical to their business. ...
None of this is relevant to what I'm trying to convey, which is simply:
What ZFS does beyond RAID.
Why are you taking the position that they are equivalent? There are
innumerable failure modes that RAID(-1) cannot handle, which ZFS does.
>
> BTW - NONE of them use zfs - because these are mainframe systems, not
> Linux. But they all use the mainframe versions of RAID-1 or RAID-10.
I still claim - along with Sun - that you can, using more modern
software, improve on the integrity and availability guarantees of
RAID-1. This applies equally to the small systems I specify (say, a
small mirrored disk server storing POS account data) as to their
humongous storage arrays.
>
> In any case - this is way off topic for this newsgroup. The original
> question was "Can I prevent the loss of a significant portion of my data
> in the case of a MySQL, OS or hardware failure, when using MyISAM?".
>
> The answer is no.
>
> --
> ==================
> Remove the "x" from my email address
> Jerry Stuckle
> JDS Computer Training Corp.
> jstucklex@attglobal.net
> ==================
|
|
|
|
|