[Beowulf] hardware RAID versus mdadm versus LVM-striping
gerry.creager at tamu.edu
Sun Jan 17 20:54:52 PST 2010
Joe Landman wrote:
> Rahul Nabar wrote:
>> On Sun, Jan 17, 2010 at 9:36 PM, Joe Landman
>> <landman at scalableinformatics.com> wrote:
>>> Ohhh ... it depends. Some of the "vendors" hardware raid ... heck
>>> ... most
>>> of it ... is rebadged LSI gear. Usually their lower end stuff which is
>>> sometimes fake-raid. Use fake-raid only if no other options exist.
>> Thanks Joe! What's "fake RAID"? Just a bad implementation or...........?
> Its a software RAID implementation pretending to be a hardware RAID
> implementation. They are rarely if ever as good as MD. Many of them in
> Linux will invoke dm (the "other" RAID engine) as dm has "support" for
> fake-raid. Note that we have lost data (multiple times) with
> dm+fake-raid in testing, so we don't recommend its use in important
> machines (ones which you can't afford to lose). This could be due to
> bad drivers for the chips in question, but we aren't taking chances.
>>> LVM is not a performance tool. Use it to help you manage things, not
>> I had thought so. But why then does LVM have features like striping if
>> not for performance? Or are they just not so good?
> LVM doesn't perform as well as MD RAID for performance. You can use it,
> just be advised that you are leaving a great deal of performance on the
> table if you do so.
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
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