Re: [exim] RAID level for mailstore

Marc Perkel wrote:
>
> Tom Brown wrote:
>> Hi
>>
>> I wonder what people think for a RAID level for their mail stores?
>>
>> I can only have RAID 1 or RAID 5 and i dont have many users ~500 so what
>> do people think? This will be on a hardware RAID card but the RAID
>> channel will not be dedicated to the mail store ie there will be another
>> RAID disk sharing the channel.
>>
>> Just want to lay the spindles out 'correctly'
>>
>>
>>
>
> Get a couple seagate baracudda drives that are 750g+ and has the 32mb
> buffer and use raid 1. It's both fast and secure assuming you need speed.
>

... also hotter-running, shorter-lived, and less reliable than proper
server-grade HDD. And 'reliable' is the first syllable of 'secure'.

Consumer/hobbyist/gamer gear (Seagrate) is not at all well-suited for 24
x 7 server use. Anyway - live video-editing and such aside, high RPM in
general is seldom worth the downside, even when 'done right' on
expensive SCSI. Too hot.

All Exim needs for 'speed' is adequate RAM, a decent OS, CPU, MB/bus and
controller, a configuration (especially w/r scanner use) that is not
terribly inefficient.

And queue, mailstore, and lookup/DB's *on different spindles/arrays*.

At which point 2 or 3 RAID1 arrays of long-lasting, cool-running 5400
RPM 2.5" HDD might surprise you w/r 'speed'.

Don't fall in love with RPM or 'best case' read/write times. It's all
about seek times.

On which score six independent head positioners vs two will eat those
big Seagrates for a snack, do it on a fraction of the wattage, need
fewer cooling fans, and run 2 or 3 times as long.

Bottleneck?

Yes - I/O from/to anything with moving parts having greater mass than an
electron has always been - will always be.

Significantly so? Or functionally limiting?
Not ordinarily even on the 'Critical Path'.

Few folks have more than a 100 mbps link *local* to the IX, or 10 mbps
*international* or 'transcontinental'. Many, if not most, of us have to
make do with a fraction of those numbers being available to the MTA.

Ergo MTA's are not generally in the high stress zone. Can't afford the
openers.

When they become so, it is more prudent to split the load than run a
hand-grenade for any one server - if only because that puts too much
reliance on one set of gear. Which WILL need off-line maintenance /
upgrades now and again even if NONE of the hardware breaks.

JM2C (plus Sod's Law, and a lot of years) Worth

Bill