Betr.: [OT] MailScanner and SSDs

[Glenn Steen]

2009/10/26 Christopher Fisk <cfisk at qwicnet.com>:
>>  2009/10/26 <Amelein at dantumadiel.eu>
>>  >
>>  > Considering the limited amount of writes you have on an
>>  SSD still I'd say that using SSD's for an MTA would not
>>  be the best idea.
>>  > Mail servers handle lots of tiny files so in that view
>>  SSD's would be perfect with their low access times,
>>  everything is possible as long as you stuff enough money
>>  into it :-)
>>  > If its just for archiving I'd suggest a raid 5 or 6
>>  array with cheap sata disks. (5 can handle 1 disk
>>  failure, 6 can handle 2, add hot spares depending on how
>>  secure you want the data)
>>  > I think the same principals apply as for a fileserver,
>>  it depends on how much file IO you are expecting to have
>>  and the kind of data on it.
>>  >
>>  (snip)
>>  Well, sure the SSD will suffer from a limited amount of
>>  writes, but
>>  the whole point of using one would be to gain
>>  performance, and to do
>>  so where it counts the most. Which means actually using
>>  the thing for
>>  write-intense things.
>>  The similar thing for an Oracle DB, for example, would be
>>  to put all
>>  control files and UNDO/REDO on the SSD
>>  (counterintuitively... goes
>>  against any OFA recomendations of old:-).
>>  Using them for read-intense things would be nice to, but
>>  a large
>>  factor less productive, from a performance perspective.
>
>>  One could reason that when one moves to having stuff on
>>  an SSD, one
>>  has moved up the budget ladder... So having to buy new
>>  ones from time
>>  to time wouldn't be a problem;-):-)
>
> If performance is that much of an issue for you where you are willing to burn through SSD's like that, you would be much better off switching the work directory to RAMDISK and putting the money you would put into SSD's into UPS's.
>
> Faster, won't wear out nearly as fast and cheaper, since you probably have the UPS's in place already.
>
>
> Christopher Fisk
>
1) I don't have a problem.
2) I don't have/use low-end SSDs for precisely this reason. They are
(still) a too expensive solution to performance problems... and not
using them as I suggest would likely NOT be a good idea, since they
(still) are too expensive/GiB to have as placeholders. Read
performance genereally is a much smaller/simpler problem to solve
(in-memory caching etc), so not really that much helped by an SSD.
3) Even with UPSes, a RAMDISK will never be secure enough for anything
but the most discardable of things (like the MS work dir).
4) If, in light of the above, one still opt for SSDs ... this implies
a budget beyond the normal... Perhaps one has a very largescale
operation? And then one could well employ the scheme mentioned.

Perhaps one should be clear about SSDs... They are NOT a homogenous
set of HW... You have everything from cheap flash cr*p, on to
elaborate things (like the Texas Memory System getups). What you both
say about wear... is only true for the "lowbudget" things;-). SSDs
have been around for ages, always a tad too expensive... and have
never been that well-defined, other than it being some form of
RAM-like memory pretending to be a disk. Note that the TMS thingies
have (all builtin) RAM for the drive part, UPS and backup drives
(RAID)... *That* is an SSD worth considering;-). And that one would
not be subject to flash memory wear considerations.

As stated in my initial response... Exactly what tradeoffs (and what
specific HW!) someone who does use SSDs would've made.... would be of
great interrest.

Cheers
-- 
-- Glenn
email: glenn < dot > steen < at > gmail < dot > com
work: glenn < dot > steen < at > ap1 < dot > se