[lug] Reliable SATA server?

[Dan Ferris]

Your IO wait time is pretty serious, looks like your server is spending 
40-50% of its time waiting for IO to complete.  My own personal rule is 
that more than 10% of IO wait continuously means you have a problem.

Do you use hardware host bus adapters with write back caching, or are 
you using plain sata drives and mdadm?

Dan

On 4/21/2012 9:03 AM, Rob Nagler wrote:
> Over the years we've struggled to find a reliable SATA server for our
> backups.  I have tried numerous versions of SATA computers, and they
> all seem to fail under our loads, always.  The failure is usually in
> the form of the computer hanging in such a bad state that it requires
> a power cycle.
>
> We do have a fairly stable server these days, but now I'm finding the
> disk slots are failing -- along with the disks.  The server isn't that
> old, but it has been relatively reliable (only the occasional hang).
>
> I've attached a vmstat when the server is busy.  I can't do much on
> the server at this time, e.g. tab completion of a command takes a few
> seconds.  This is very different from a benchmark load so the numbers
> are deceptive.
>
> At this stage, I'm tempted to bite the bullet and go with SAS.  We
> have SCSI3 machines running with heavy (but dissimilar) loads without
> a problem.
>
> I've asked this question on this list before, and not gotten a
> satisfactory answer.  Nobody seems to run the same type of loads that
> we do, and all their servers run just fine.  However, if you do have
> experience with non-sequential writing of large amounts of data to
> on a SATA server, please let me know.
>
> Thanks,
> Rob
>
> # vmstat 1
> procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
>   r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
>   0  2    144  15672 328852 826992    0    0   300   184    9    3  2  1 91  6  0
>   0  2    144  16136 328436 827052    0    0  3684     0 1544 1361  3  2 55 39  0
>   0  2    144  19764 326164 826964    0    0 10948     0 1270 1253 10  2 52 37  0
>   2  1    144  26640 321224 826268    0    0 27828  2948 1295 2364 21  3 50 26  0
>   0  2    144  26504 320472 827268    0    0  5832     0 1375 1150 10  1 54 35  0
>   0  3    144  29356 319048 826360    0    0  4688   784 1371  984 13  2 52 33  0
>   0  3    144  29232 319048 826528    0    0    32  5624 1114   90  0  0 62 37  0
>   0  2    144  29232 319048 826508    0    0     8   748 1119   72  0  0 54 46  0
>   0  3    144  29232 319052 826532    0    0     8    36 1094   56  0  0 26 74  0
>   0  2    144  29608 318708 826432    0    0  3244     4 1446 1138  3  2 52 43  0
>   0  2    144  29884 318204 826952    0    0  2344  1000 1294  656  2  1 55 42  0
>   1  2    144  32428 316516 826648    0    0  6388     0 1167  732 10  2 49 40  0
>   1  2    144  35916 314220 825756    0    0  7476     0 1205  837 11  2 49 38  0
>   0  2    144  37940 312616 825584    0    0  6484     0 1228  835 10  2 49 40  0
>   0  2    144  39108 311712 825816    0    0  4184 14048 1235  553  5  1 50 44  0
>   0  3    144  39428 310848 826544    0    0  4528  4956 1333  939  6  2 53 40  0
>   0  3    144  39428 310852 826676    0    0     8   784 1131   80  0  0 51 49  0
>   0  2    144  39428 310852 826644    0    0     8   468 1099   78  0  0 50 50  0
>   0  2    144  40328 310620 825876    0    0   912     0 1338  694  0  0 52 48  0
>   0  2    144  39600 310476 826804    0    0  3092   104 1492 1285  1  2 60 37  0
>   0  2    144  40972 309896 826492    0    0  3636  1052 1312  806  3  1 54 42  0
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