From: Zdenek Kabelac <zdenek.kabelac@gmail.com>
To: LVM general discussion and development <linux-lvm@redhat.com>,
Oleg Cherkasov <o1e9@member.fsf.org>,
John Stoffel <john@stoffel.org>
Subject: Re: [linux-lvm] cache on SSD makes system unresponsive
Date: Mon, 23 Oct 2017 12:58:09 +0200 [thread overview]
Message-ID: <8bacff07-dd78-ef2d-6294-048ef8e92b06@gmail.com> (raw)
In-Reply-To: <88f3c8a9-8c55-a74f-c9cb-4b8aa18a28fc@member.fsf.org>
Dne 21.10.2017 v 16:33 Oleg Cherkasov napsal(a):
> On 20. okt. 2017 21:35, John Stoffel wrote:
>>>>>>> "Oleg" == Oleg Cherkasov <o1e9@member.fsf.org> writes:
>>
>> Oleg> On 19. okt. 2017 21:09, John Stoffel wrote:
>>>>
>>
>> Oleg> RAM 12Gb, swap around 12Gb as well.� /dev/sda is a hardware RAID1, the
>> Oleg> rest are RAID5.
>>
>> Interesting, it's all hardware RAID devices from what I can see.
>
> It is exactly what I wrote initially in my first message!
>
>>
>> Can you should the *exact* commands you used to make the cache?� Are
>> you using lvcache, or bcache?� they're two totally different beasts.
>> I looked into bcache in the past, but since you can't remove it from
>> an LV, I decided not to use it.� I use lvcache like this:
>
> I have used lvcache of course and here are commands from bash history:
>
> lvcreate -L 1G -n primary_backup_lv_cache_meta primary_backup_vg /dev/sda5
>
> ### Allocate ~247G ib /dev/sda5 what has left of VG
> lvcreate -l 100%FREE -n primary_backup_lv_cache primary_backup_vg /dev/sda5
>
> lvconvert --type cache-pool --cachemode writethrough --poolmetadata
> primary_backup_vg/primary_backup_lv_cache_meta
> primary_backup_vg/primary_backup_lv_cache
>
> lvconvert --type cache --cachepool primary_backup_vg/primary_backup_lv_cache
> primary_backup_vg/primary_backup_lv
>
> ### lvconvert failed because required some extra extends in VG so I had to
> reduce cache LV and try again:
>
> lvreduce -L 200M primary_backup_vg/primary_backup_lv_cache
>
Hi
Without plans to interrupt thoughts on topic here - the explanation here is
very simple.
Cache pool is made from 'data' & 'metadata' LV - so both needs some space.
In the case of 'cache pool' it's pretty good plan to have both device is fast
spindle (SSD).
So can you please provide output of:
lvs -a -o+devices
so it could be easily validated both _cdata & _cmeta LV is hosted by some SSD
device (it's not shown anywhere in the thread - so just to be sure we have
them on right disks)
Regards
Zdenek
next prev parent reply other threads:[~2017-10-23 10:58 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-19 17:54 [linux-lvm] cache on SSD makes system unresponsive Oleg Cherkasov
2017-10-19 18:13 ` Xen
2017-10-20 10:21 ` Oleg Cherkasov
2017-10-20 10:38 ` Xen
2017-10-20 11:41 ` Oleg Cherkasov
2017-10-19 18:49 ` Mike Snitzer
2017-10-20 11:07 ` Joe Thornber
2017-10-19 19:09 ` John Stoffel
2017-10-19 19:46 ` Xen
2017-10-19 21:14 ` John Stoffel
2017-10-20 6:42 ` Xen
2017-10-19 21:59 ` Oleg Cherkasov
2017-10-20 19:35 ` John Stoffel
2017-10-21 3:05 ` Mike Snitzer
2017-10-21 14:33 ` Oleg Cherkasov
2017-10-23 10:58 ` Zdenek Kabelac [this message]
2017-10-21 2:55 ` Mike Snitzer
2017-10-21 14:10 ` Oleg Cherkasov
2017-10-23 20:45 ` John Stoffel
2017-10-20 16:20 ` lejeczek
2017-10-20 16:48 ` Xen
2017-10-20 17:02 ` Bernd Eckenfels
2017-10-24 14:51 ` lejeczek
[not found] <640472762.2746512.1508882485777.ref@mail.yahoo.com>
2017-10-24 22:01 ` matthew patton
2017-10-24 23:10 ` Chris Friesen
[not found] <1928541660.2031191.1508802005006.ref@mail.yahoo.com>
2017-10-23 23:40 ` matthew patton
2017-10-24 15:36 ` Xen
[not found] <1714773615.1945146.1508792555922.ref@mail.yahoo.com>
2017-10-23 21:02 ` matthew patton
2017-10-23 21:54 ` Xen
2017-10-24 2:51 ` John Stoffel
[not found] <1540708205.1077645.1508602122091.ref@mail.yahoo.com>
2017-10-21 16:08 ` matthew patton
[not found] <1244564108.1073508.1508601932111.ref@mail.yahoo.com>
2017-10-21 16:05 ` matthew patton
2017-10-24 18:09 ` Oleg Cherkasov
[not found] <541215543.377417.1508458336923.ref@mail.yahoo.com>
2017-10-20 0:12 ` matthew patton
2017-10-20 6:46 ` Xen
2017-10-20 9:59 ` Oleg Cherkasov
-- strict thread matches above, loose matches on Subject: below --
2017-10-19 10:05 Oleg Cherkasov
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